[cc] Calculate the correct latest_confirmed_sequence_number in cc::Scheduler.

cc/scheduler/scheduler_state_machine_unittest.cc

 // Copyright 2011 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "cc/scheduler/scheduler_state_machine.h"
 
 #include <stddef.h>
 
 #include "base/trace_event/trace_event.h"
+#include "cc/output/begin_frame_args.h"
 #include "cc/scheduler/scheduler.h"
 #include "cc/test/begin_frame_args_test.h"
 #include "testing/gtest/include/gtest/gtest.h"
 
 // Macro to compare two enum values and get nice output.
 // Without:
 //   Value of: actual()      Actual: 7
 //   Expected: expected()  Which is: 0
 // With:
 //   Value of: actual()      Actual: "ACTION_DRAW"
 //   Expected: expected()  Which is: "ACTION_NONE"
 #define EXPECT_ENUM_EQ(enum_tostring, expected, actual)        \
   EXPECT_STREQ(SchedulerStateMachine::enum_tostring(expected), \
                SchedulerStateMachine::enum_tostring(actual))
 
+#define EXPECT_SEQUENCE_NUMBERS(current, main_frame, pending_tree,            \
+                                active_tree, compositor_frame)                \
+  EXPECT_EQ(current, state.begin_frame_sequence_number());                    \
+  EXPECT_EQ(main_frame,                                                       \
+            state.last_begin_frame_sequence_number_begin_main_frame_sent());  \
+  EXPECT_EQ(pending_tree,                                                     \
+            state.last_begin_frame_sequence_number_pending_tree_was_fresh()); \
+  EXPECT_EQ(active_tree,                                                      \
+            state.last_begin_frame_sequence_number_active_tree_was_fresh());  \
+  EXPECT_EQ(                                                                  \
+      compositor_frame,                                                       \
+      state.last_begin_frame_sequence_number_compositor_frame_was_fresh())
+
 #define EXPECT_IMPL_FRAME_STATE(expected)               \
   EXPECT_ENUM_EQ(BeginImplFrameStateToString, expected, \
                  state.begin_impl_frame_state())        \
       << state.AsValue()->ToString()
 
 #define EXPECT_MAIN_FRAME_STATE(expected)               \
   EXPECT_ENUM_EQ(BeginMainFrameStateToString, expected, \
                  state.BeginMainFrameState())
 
 #define EXPECT_ACTION(expected)                                \
@@ skipping 44 matching lines @@
  public:
   explicit StateMachine(const SchedulerSettings& scheduler_settings)
       : SchedulerStateMachine(scheduler_settings),
         draw_result_for_test_(DRAW_SUCCESS) {}
 
   void CreateAndInitializeCompositorFrameSinkWithActivatedCommit() {
     DidCreateAndInitializeCompositorFrameSink();
     compositor_frame_sink_state_ = COMPOSITOR_FRAME_SINK_ACTIVE;
   }
 
+  void IssueNextBeginImplFrame() {
+    OnBeginImplFrame(0, next_begin_frame_number_++);
+  }
+
   void SetBeginMainFrameState(BeginMainFrameState cs) {
     begin_main_frame_state_ = cs;
   }
   BeginMainFrameState BeginMainFrameState() const {
     return begin_main_frame_state_;
   }
 
   ForcedRedrawOnTimeoutState ForcedRedrawState() const {
     return forced_redraw_state_;
   }
@@ skipping 44 matching lines @@
 
   bool PendingActivationsShouldBeForced() const {
     return SchedulerStateMachine::PendingActivationsShouldBeForced();
   }
 
   bool has_pending_tree() const { return has_pending_tree_; }
   void SetHasPendingTree(bool has_pending_tree) {
     has_pending_tree_ = has_pending_tree;
   }
 
+  uint64_t begin_frame_sequence_number() const {
+    return begin_frame_sequence_number_;
+  }
+  uint64_t last_begin_frame_sequence_number_begin_main_frame_sent() const {
+    return last_begin_frame_sequence_number_begin_main_frame_sent_;
+  }
+  uint64_t last_begin_frame_sequence_number_pending_tree_was_fresh() const {
+    return last_begin_frame_sequence_number_pending_tree_was_fresh_;
+  }
+  uint64_t last_begin_frame_sequence_number_active_tree_was_fresh() const {
+    return last_begin_frame_sequence_number_active_tree_was_fresh_;
+  }
+
   using SchedulerStateMachine::ShouldTriggerBeginImplFrameDeadlineImmediately;
   using SchedulerStateMachine::ProactiveBeginFrameWanted;
   using SchedulerStateMachine::WillCommit;
 
  protected:
   DrawResult draw_result_for_test_;
+  uint64_t next_begin_frame_number_ = BeginFrameArgs::kStartingFrameNumber;
 };
 
 void PerformAction(StateMachine* sm, SchedulerStateMachine::Action action) {
   switch (action) {
     case SchedulerStateMachine::ACTION_NONE:
       return;
 
     case SchedulerStateMachine::ACTION_ACTIVATE_SYNC_TREE:
       sm->WillActivate();
       return;
@@ skipping 95 matching lines @@
         SchedulerStateMachine::ACTION_BEGIN_COMPOSITOR_FRAME_SINK_CREATION);
     EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_NONE);
     state.CreateAndInitializeCompositorFrameSinkWithActivatedCommit();
     state.SetBeginMainFrameState(
         SchedulerStateMachine::BEGIN_MAIN_FRAME_STATE_IDLE);
     state.SetNeedsRedraw(false);
 
     EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_NONE);
     EXPECT_FALSE(state.NeedsCommit());
 
-    state.OnBeginImplFrame();
+    state.IssueNextBeginImplFrame();
     EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_NONE);
 
     state.OnBeginImplFrameDeadline();
     EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_NONE);
     EXPECT_FALSE(state.NeedsCommit());
   }
 
   // If commit requested but not visible yet, do nothing.
   {
     StateMachine state(default_scheduler_settings);
     state.SetBeginMainFrameState(
         SchedulerStateMachine::BEGIN_MAIN_FRAME_STATE_IDLE);
     state.SetNeedsRedraw(false);
     state.SetNeedsBeginMainFrame();
 
     EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_NONE);
     EXPECT_TRUE(state.NeedsCommit());
 
-    state.OnBeginImplFrame();
+    state.IssueNextBeginImplFrame();
     EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_NONE);
 
     state.OnBeginImplFrameDeadline();
     EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_NONE);
     EXPECT_TRUE(state.NeedsCommit());
   }
 
   // If commit requested, begin a main frame.
   {
     StateMachine state(default_scheduler_settings);
     state.SetBeginMainFrameState(
         SchedulerStateMachine::BEGIN_MAIN_FRAME_STATE_IDLE);
     state.SetVisible(true);
     EXPECT_ACTION_UPDATE_STATE(
         SchedulerStateMachine::ACTION_BEGIN_COMPOSITOR_FRAME_SINK_CREATION);
     EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_NONE);
     state.CreateAndInitializeCompositorFrameSinkWithActivatedCommit();
     state.SetNeedsRedraw(false);
     state.SetNeedsBeginMainFrame();
 
     // Expect nothing to happen until after OnBeginImplFrame.
     EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_NONE);
     EXPECT_MAIN_FRAME_STATE(SchedulerStateMachine::BEGIN_MAIN_FRAME_STATE_IDLE);
     EXPECT_IMPL_FRAME_STATE(SchedulerStateMachine::BEGIN_IMPL_FRAME_STATE_IDLE);
     EXPECT_TRUE(state.NeedsCommit());
     EXPECT_TRUE(state.BeginFrameNeeded());
 
-    state.OnBeginImplFrame();
+    state.IssueNextBeginImplFrame();
     EXPECT_ACTION_UPDATE_STATE(
         SchedulerStateMachine::ACTION_SEND_BEGIN_MAIN_FRAME);
     EXPECT_MAIN_FRAME_STATE(SchedulerStateMachine::BEGIN_MAIN_FRAME_STATE_SENT);
     EXPECT_FALSE(state.NeedsCommit());
   }
 
   // If commit requested and can't draw, still begin a main frame.
   {
     StateMachine state(default_scheduler_settings);
     state.SetBeginMainFrameState(
         SchedulerStateMachine::BEGIN_MAIN_FRAME_STATE_IDLE);
     state.SetVisible(true);
     EXPECT_ACTION_UPDATE_STATE(
         SchedulerStateMachine::ACTION_BEGIN_COMPOSITOR_FRAME_SINK_CREATION);
     EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_NONE);
     state.CreateAndInitializeCompositorFrameSinkWithActivatedCommit();
     state.SetNeedsRedraw(false);
     state.SetNeedsBeginMainFrame();
     state.SetCanDraw(false);
 
     // Expect nothing to happen until after OnBeginImplFrame.
     EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_NONE);
     EXPECT_MAIN_FRAME_STATE(SchedulerStateMachine::BEGIN_MAIN_FRAME_STATE_IDLE);
     EXPECT_IMPL_FRAME_STATE(SchedulerStateMachine::BEGIN_IMPL_FRAME_STATE_IDLE);
     EXPECT_TRUE(state.BeginFrameNeeded());
 
-    state.OnBeginImplFrame();
+    state.IssueNextBeginImplFrame();
     EXPECT_ACTION_UPDATE_STATE(
         SchedulerStateMachine::ACTION_SEND_BEGIN_MAIN_FRAME);
     EXPECT_MAIN_FRAME_STATE(SchedulerStateMachine::BEGIN_MAIN_FRAME_STATE_SENT);
     EXPECT_FALSE(state.NeedsCommit());
   }
 }
 
 // Explicitly test main_frame_before_activation_enabled = true
 TEST(SchedulerStateMachineTest, MainFrameBeforeActivationEnabled) {
   SchedulerSettings scheduler_settings;
   scheduler_settings.main_frame_before_activation_enabled = true;
   StateMachine state(scheduler_settings);
   state.SetBeginMainFrameState(
       SchedulerStateMachine::BEGIN_MAIN_FRAME_STATE_IDLE);
   SET_UP_STATE(state)
   state.SetNeedsRedraw(false);
   state.SetNeedsBeginMainFrame();
 
   EXPECT_TRUE(state.BeginFrameNeeded());
 
   // Commit to the pending tree.
-  state.OnBeginImplFrame();
+  state.IssueNextBeginImplFrame();
   EXPECT_ACTION_UPDATE_STATE(
       SchedulerStateMachine::ACTION_SEND_BEGIN_MAIN_FRAME);
   EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_NONE);
 
   state.NotifyBeginMainFrameStarted();
   state.NotifyReadyToCommit();
   EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_COMMIT);
   EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_NONE);
   EXPECT_MAIN_FRAME_STATE(SchedulerStateMachine::BEGIN_MAIN_FRAME_STATE_IDLE);
 
   state.OnBeginImplFrameDeadline();
   EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_NONE);
 
   // Verify that the next commit starts while there is still a pending tree.
   state.SetNeedsBeginMainFrame();
-  state.OnBeginImplFrame();
+  state.IssueNextBeginImplFrame();
   EXPECT_ACTION_UPDATE_STATE(
       SchedulerStateMachine::ACTION_SEND_BEGIN_MAIN_FRAME);
   EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_NONE);
 
   // Verify the pending commit doesn't overwrite the pending
   // tree until the pending tree has been activated.
   state.NotifyBeginMainFrameStarted();
   state.NotifyReadyToCommit();
   EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_NONE);
 
@@ skipping 16 matching lines @@
 TEST(SchedulerStateMachineTest,
      FailedDrawForAnimationCheckerboardSetsNeedsCommitAndRetriesDraw) {
   SchedulerSettings default_scheduler_settings;
   StateMachine state(default_scheduler_settings);
   SET_UP_STATE(state)
   state.SetNeedsRedraw(true);
   EXPECT_TRUE(state.RedrawPending());
   EXPECT_TRUE(state.BeginFrameNeeded());
 
   // Start a frame.
-  state.OnBeginImplFrame();
+  state.IssueNextBeginImplFrame();
   EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_NONE);
   EXPECT_FALSE(state.CommitPending());
 
   // Failing a draw triggers request for a new BeginMainFrame.
   state.OnBeginImplFrameDeadline();
   state.SetDrawResultForTest(DRAW_ABORTED_CHECKERBOARD_ANIMATIONS);
   EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_DRAW_IF_POSSIBLE);
   EXPECT_ACTION_UPDATE_STATE(
       SchedulerStateMachine::ACTION_SEND_BEGIN_MAIN_FRAME);
   EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_NONE);
   state.OnBeginImplFrameIdle();
   EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_NONE);
 
   // It's okay to attempt more draws just in case additional raster
   // finishes and the requested commit wasn't actually necessary.
   EXPECT_TRUE(state.CommitPending());
   EXPECT_TRUE(state.RedrawPending());
-  state.OnBeginImplFrame();
+  state.IssueNextBeginImplFrame();
   EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_NONE);
   state.OnBeginImplFrameDeadline();
   state.SetDrawResultForTest(DRAW_ABORTED_CHECKERBOARD_ANIMATIONS);
   EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_DRAW_IF_POSSIBLE);
   EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_NONE);
   state.OnBeginImplFrameIdle();
   EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_NONE);
 }
 
 TEST(SchedulerStateMachineTest, FailedDrawForMissingHighResNeedsCommit) {
   SchedulerSettings default_scheduler_settings;
   StateMachine state(default_scheduler_settings);
   SET_UP_STATE(state)
   state.SetNeedsRedraw(true);
   EXPECT_TRUE(state.RedrawPending());
   EXPECT_TRUE(state.BeginFrameNeeded());
 
   // Start a frame.
-  state.OnBeginImplFrame();
+  state.IssueNextBeginImplFrame();
   EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_NONE);
   EXPECT_FALSE(state.CommitPending());
 
   // Failing a draw triggers because of high res tiles missing
   // request for a new BeginMainFrame.
   state.OnBeginImplFrameDeadline();
   state.SetDrawResultForTest(DRAW_ABORTED_MISSING_HIGH_RES_CONTENT);
   EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_DRAW_IF_POSSIBLE);
   EXPECT_ACTION_UPDATE_STATE(
       SchedulerStateMachine::ACTION_SEND_BEGIN_MAIN_FRAME);
   EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_NONE);
   state.OnBeginImplFrameIdle();
   EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_NONE);
 
   // It doesn't request a draw until we get a new commit though.
   EXPECT_TRUE(state.CommitPending());
   EXPECT_FALSE(state.RedrawPending());
-  state.OnBeginImplFrame();
+  state.IssueNextBeginImplFrame();
   EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_NONE);
   state.OnBeginImplFrameDeadline();
   EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_NONE);
   state.OnBeginImplFrameIdle();
   EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_NONE);
 
   // Finish the commit and activation.
   state.NotifyBeginMainFrameStarted();
   state.NotifyReadyToCommit();
   EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_COMMIT);
   EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_NONE);
   state.NotifyReadyToActivate();
   EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_ACTIVATE_SYNC_TREE);
   EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_NONE);
   EXPECT_TRUE(state.RedrawPending());
 
   // Verify we draw with the new frame.
-  state.OnBeginImplFrame();
+  state.IssueNextBeginImplFrame();
   EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_NONE);
   state.OnBeginImplFrameDeadline();
   state.SetDrawResultForTest(DRAW_SUCCESS);
   EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_DRAW_IF_POSSIBLE);
   state.DidSubmitCompositorFrame();
   EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_NONE);
   state.OnBeginImplFrameIdle();
   EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_NONE);
 }
 
 TEST(SchedulerStateMachineTest,
      TestFailedDrawsEventuallyForceDrawAfterNextCommit) {
   SchedulerSettings scheduler_settings;
   scheduler_settings.maximum_number_of_failed_draws_before_draw_is_forced = 1;
   StateMachine state(scheduler_settings);
   SET_UP_STATE(state)
 
   // Start a commit.
   state.SetNeedsBeginMainFrame();
   EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_NONE);
-  state.OnBeginImplFrame();
+  state.IssueNextBeginImplFrame();
   EXPECT_ACTION_UPDATE_STATE(
       SchedulerStateMachine::ACTION_SEND_BEGIN_MAIN_FRAME);
   EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_NONE);
   EXPECT_TRUE(state.CommitPending());
 
   // Then initiate a draw that fails.
   state.SetNeedsRedraw(true);
   state.OnBeginImplFrameDeadline();
   state.SetDrawResultForTest(DRAW_ABORTED_CHECKERBOARD_ANIMATIONS);
   EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_DRAW_IF_POSSIBLE);
@@ skipping 10 matching lines @@
   EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_NONE);
   EXPECT_TRUE(state.RedrawPending());
 
   // Activate so we're ready for a new main frame.
   state.NotifyReadyToActivate();
   EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_ACTIVATE_SYNC_TREE);
   EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_NONE);
   EXPECT_TRUE(state.RedrawPending());
 
   // The redraw should be forced at the end of the next BeginImplFrame.
-  state.OnBeginImplFrame();
+  state.IssueNextBeginImplFrame();
   EXPECT_ACTION_UPDATE_STATE(
       SchedulerStateMachine::ACTION_SEND_BEGIN_MAIN_FRAME);
   EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_NONE);
   state.OnBeginImplFrameDeadline();
   state.SetDrawResultForTest(DRAW_SUCCESS);
   EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_DRAW_FORCED);
   state.DidSubmitCompositorFrame();
   EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_NONE);
   state.DidReceiveCompositorFrameAck();
   EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_NONE);
 }
 
 TEST(SchedulerStateMachineTest, TestFailedDrawsDoNotRestartForcedDraw) {
   SchedulerSettings scheduler_settings;
   int draw_limit = 2;
   scheduler_settings.maximum_number_of_failed_draws_before_draw_is_forced =
       draw_limit;
   StateMachine state(scheduler_settings);
   SET_UP_STATE(state)
 
   // Start a commit.
   state.SetNeedsBeginMainFrame();
   EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_NONE);
-  state.OnBeginImplFrame();
+  state.IssueNextBeginImplFrame();
   EXPECT_ACTION_UPDATE_STATE(
       SchedulerStateMachine::ACTION_SEND_BEGIN_MAIN_FRAME);
   EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_NONE);
   EXPECT_TRUE(state.CommitPending());
 
   // Then initiate a draw.
   state.SetNeedsRedraw(true);
   state.OnBeginImplFrameDeadline();
   EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_DRAW_IF_POSSIBLE);
 
   // Fail the draw enough times to force a redraw.
   for (int i = 0; i < draw_limit; ++i) {
     state.SetNeedsRedraw(true);
-    state.OnBeginImplFrame();
+    state.IssueNextBeginImplFrame();
     EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_NONE);
     state.OnBeginImplFrameDeadline();
     state.SetDrawResultForTest(DRAW_ABORTED_CHECKERBOARD_ANIMATIONS);
     EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_DRAW_IF_POSSIBLE);
     EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_NONE);
     state.OnBeginImplFrameIdle();
     EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_NONE);
   }
 
   EXPECT_TRUE(state.BeginFrameNeeded());
   EXPECT_TRUE(state.RedrawPending());
   // But the commit is ongoing.
   EXPECT_TRUE(state.CommitPending());
   EXPECT_TRUE(state.ForcedRedrawState() ==
               SchedulerStateMachine::FORCED_REDRAW_STATE_WAITING_FOR_COMMIT);
 
   // After failing additional draws, we should still be in a forced
   // redraw, but not back in IDLE.
   for (int i = 0; i < draw_limit; ++i) {
     state.SetNeedsRedraw(true);
-    state.OnBeginImplFrame();
+    state.IssueNextBeginImplFrame();
     EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_NONE);
     state.OnBeginImplFrameDeadline();
     state.SetDrawResultForTest(DRAW_ABORTED_CHECKERBOARD_ANIMATIONS);
     EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_DRAW_IF_POSSIBLE);
     EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_NONE);
     state.OnBeginImplFrameIdle();
     EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_NONE);
   }
   EXPECT_TRUE(state.RedrawPending());
   EXPECT_TRUE(state.ForcedRedrawState() ==
               SchedulerStateMachine::FORCED_REDRAW_STATE_WAITING_FOR_COMMIT);
 }
 
 TEST(SchedulerStateMachineTest, TestFailedDrawIsRetriedInNextBeginImplFrame) {
   SchedulerSettings default_scheduler_settings;
   StateMachine state(default_scheduler_settings);
   SET_UP_STATE(state)
 
   // Start a draw.
   state.SetNeedsRedraw(true);
   EXPECT_TRUE(state.BeginFrameNeeded());
-  state.OnBeginImplFrame();
+  state.IssueNextBeginImplFrame();
   EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_NONE);
   state.OnBeginImplFrameDeadline();
   EXPECT_TRUE(state.RedrawPending());
   state.SetDrawResultForTest(DRAW_ABORTED_CHECKERBOARD_ANIMATIONS);
   EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_DRAW_IF_POSSIBLE);
 
   // Failing the draw for animation checkerboards makes us require a commit.
   EXPECT_ACTION_UPDATE_STATE(
       SchedulerStateMachine::ACTION_SEND_BEGIN_MAIN_FRAME);
   EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_NONE);
   EXPECT_TRUE(state.RedrawPending());
 
   // We should not be trying to draw again now, but we have a commit pending.
   EXPECT_TRUE(state.BeginFrameNeeded());
-  state.OnBeginImplFrame();
+  state.IssueNextBeginImplFrame();
   EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_NONE);
 
   // We should try to draw again at the end of the next BeginImplFrame on
   // the impl thread.
   state.OnBeginImplFrameDeadline();
   state.SetDrawResultForTest(DRAW_SUCCESS);
   EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_DRAW_IF_POSSIBLE);
   state.DidSubmitCompositorFrame();
   state.DidReceiveCompositorFrameAck();
   EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_NONE);
 }
 
 TEST(SchedulerStateMachineTest, TestDoestDrawTwiceInSameFrame) {
   SchedulerSettings default_scheduler_settings;
   StateMachine state(default_scheduler_settings);
   SET_UP_STATE(state)
   state.SetNeedsRedraw(true);
 
   // Draw the first frame.
   EXPECT_TRUE(state.BeginFrameNeeded());
-  state.OnBeginImplFrame();
+  state.IssueNextBeginImplFrame();
   EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_NONE);
 
   state.OnBeginImplFrameDeadline();
   EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_DRAW_IF_POSSIBLE);
   state.DidSubmitCompositorFrame();
   state.DidReceiveCompositorFrameAck();
   EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_NONE);
 
   // Before the next BeginImplFrame, set needs redraw again.
   // This should not redraw until the next BeginImplFrame.
   state.SetNeedsRedraw(true);
   EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_NONE);
 
   // Move to another frame. This should now draw.
   EXPECT_TRUE(state.BeginFrameNeeded());
-  state.OnBeginImplFrame();
+  state.IssueNextBeginImplFrame();
   EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_NONE);
   state.OnBeginImplFrameDeadline();
   EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_DRAW_IF_POSSIBLE);
   state.DidSubmitCompositorFrame();
   state.DidReceiveCompositorFrameAck();
   EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_NONE);
 
   // We just submitted, so we should proactively request another BeginImplFrame.
   EXPECT_TRUE(state.BeginFrameNeeded());
 }
@@ skipping 117 matching lines @@
       StateMachine state(default_scheduler_settings);
       state.SetVisible(true);
       EXPECT_ACTION_UPDATE_STATE(
           SchedulerStateMachine::ACTION_BEGIN_COMPOSITOR_FRAME_SINK_CREATION);
       EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_NONE);
       state.CreateAndInitializeCompositorFrameSinkWithActivatedCommit();
       state.SetBeginMainFrameState(begin_main_frame_states[i]);
       state.SetVisible(false);
       state.SetNeedsRedraw(true);
       if (j == 1)
-        state.OnBeginImplFrame();
+        state.IssueNextBeginImplFrame();
 
       state.SetCanDraw(false);
       EXPECT_NE(SchedulerStateMachine::ACTION_DRAW_IF_POSSIBLE,
                 state.NextAction());
     }
   }
 }
 
 TEST(SchedulerStateMachineTest,
      TestCanRedrawWithWaitingForFirstDrawMakesProgress) {
   SchedulerSettings default_scheduler_settings;
   StateMachine state(default_scheduler_settings);
   state.SetVisible(true);
   EXPECT_ACTION_UPDATE_STATE(
       SchedulerStateMachine::ACTION_BEGIN_COMPOSITOR_FRAME_SINK_CREATION);
   EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_NONE);
   state.CreateAndInitializeCompositorFrameSinkWithActivatedCommit();
 
   state.SetActiveTreeNeedsFirstDraw(true);
   state.SetNeedsBeginMainFrame();
   state.SetNeedsRedraw(true);
   state.SetCanDraw(false);
-  state.OnBeginImplFrame();
+  state.IssueNextBeginImplFrame();
   EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_DRAW_ABORT);
   EXPECT_ACTION_UPDATE_STATE(
       SchedulerStateMachine::ACTION_SEND_BEGIN_MAIN_FRAME);
   EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_NONE);
   state.NotifyBeginMainFrameStarted();
   state.NotifyReadyToCommit();
   EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_COMMIT);
   state.NotifyReadyToActivate();
   EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_ACTIVATE_SYNC_TREE);
   state.OnBeginImplFrameDeadline();
   EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_DRAW_ABORT);
   EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_NONE);
 }
 
 TEST(SchedulerStateMachineTest, TestSetNeedsBeginMainFrameIsNotLost) {
   SchedulerSettings scheduler_settings;
   StateMachine state(scheduler_settings);
   SET_UP_STATE(state)
   state.SetNeedsBeginMainFrame();
 
   EXPECT_TRUE(state.BeginFrameNeeded());
 
   // Begin the frame.
-  state.OnBeginImplFrame();
+  state.IssueNextBeginImplFrame();
   EXPECT_ACTION_UPDATE_STATE(
       SchedulerStateMachine::ACTION_SEND_BEGIN_MAIN_FRAME);
   EXPECT_MAIN_FRAME_STATE(SchedulerStateMachine::BEGIN_MAIN_FRAME_STATE_SENT);
 
   // Now, while the frame is in progress, set another commit.
   state.SetNeedsBeginMainFrame();
   EXPECT_TRUE(state.NeedsCommit());
 
   // Let the frame finish.
   state.NotifyBeginMainFrameStarted();
   state.NotifyReadyToCommit();
   EXPECT_MAIN_FRAME_STATE(
       SchedulerStateMachine::BEGIN_MAIN_FRAME_STATE_READY_TO_COMMIT);
 
   // Expect to commit regardless of BeginImplFrame state.
   EXPECT_IMPL_FRAME_STATE(
       SchedulerStateMachine::BEGIN_IMPL_FRAME_STATE_INSIDE_BEGIN_FRAME);
   EXPECT_ACTION(SchedulerStateMachine::ACTION_COMMIT);
 
   state.OnBeginImplFrameDeadline();
   EXPECT_IMPL_FRAME_STATE(
       SchedulerStateMachine::BEGIN_IMPL_FRAME_STATE_INSIDE_DEADLINE);
   EXPECT_ACTION(SchedulerStateMachine::ACTION_COMMIT);
 
   state.OnBeginImplFrameIdle();
   EXPECT_IMPL_FRAME_STATE(SchedulerStateMachine::BEGIN_IMPL_FRAME_STATE_IDLE);
   EXPECT_ACTION(SchedulerStateMachine::ACTION_COMMIT);
 
-  state.OnBeginImplFrame();
+  state.IssueNextBeginImplFrame();
   EXPECT_IMPL_FRAME_STATE(
       SchedulerStateMachine::BEGIN_IMPL_FRAME_STATE_INSIDE_BEGIN_FRAME);
   EXPECT_ACTION(SchedulerStateMachine::ACTION_COMMIT);
 
   // Finish the commit and activate, then make sure we start the next commit
   // immediately and draw on the next BeginImplFrame.
   EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_COMMIT);
   state.NotifyReadyToActivate();
   EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_ACTIVATE_SYNC_TREE);
   EXPECT_ACTION_UPDATE_STATE(
@@ skipping 11 matching lines @@
 
 TEST(SchedulerStateMachineTest, TestFullCycle) {
   SchedulerSettings default_scheduler_settings;
   StateMachine state(default_scheduler_settings);
   SET_UP_STATE(state)
 
   // Start clean and set commit.
   state.SetNeedsBeginMainFrame();
 
   // Begin the frame.
-  state.OnBeginImplFrame();
+  state.IssueNextBeginImplFrame();
   EXPECT_ACTION_UPDATE_STATE(
       SchedulerStateMachine::ACTION_SEND_BEGIN_MAIN_FRAME);
   EXPECT_MAIN_FRAME_STATE(SchedulerStateMachine::BEGIN_MAIN_FRAME_STATE_SENT);
   EXPECT_FALSE(state.NeedsCommit());
   EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_NONE);
 
   // Tell the scheduler the frame finished.
   state.NotifyBeginMainFrameStarted();
   state.NotifyReadyToCommit();
   EXPECT_MAIN_FRAME_STATE(
@@ skipping 25 matching lines @@
 
 TEST(SchedulerStateMachineTest, CommitWithoutDrawWithPendingTree) {
   SchedulerSettings default_scheduler_settings;
   StateMachine state(default_scheduler_settings);
   SET_UP_STATE(state)
 
   // Start clean and set commit.
   state.SetNeedsBeginMainFrame();
 
   // Make a main frame, commit and activate it. But don't draw it.
-  state.OnBeginImplFrame();
+  state.IssueNextBeginImplFrame();
   EXPECT_ACTION_UPDATE_STATE(
       SchedulerStateMachine::ACTION_SEND_BEGIN_MAIN_FRAME);
   state.NotifyBeginMainFrameStarted();
   state.NotifyReadyToCommit();
   EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_COMMIT);
   state.NotifyReadyToActivate();
   EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_ACTIVATE_SYNC_TREE);
 
   // Try to make a new main frame before drawing. Since we will commit it to a
   // pending tree and not clobber the active tree, we're able to start a new
   // begin frame and commit it.
   state.SetNeedsBeginMainFrame();
-  state.OnBeginImplFrame();
+  state.IssueNextBeginImplFrame();
   EXPECT_ACTION_UPDATE_STATE(
       SchedulerStateMachine::ACTION_SEND_BEGIN_MAIN_FRAME);
   state.NotifyBeginMainFrameStarted();
   state.NotifyReadyToCommit();
   EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_COMMIT);
 }
 
 TEST(SchedulerStateMachineTest, DontCommitWithoutDrawWithoutPendingTree) {
   SchedulerSettings scheduler_settings;
   scheduler_settings.commit_to_active_tree = true;
   scheduler_settings.main_frame_before_activation_enabled = false;
   StateMachine state(scheduler_settings);
   SET_UP_STATE(state)
 
   // Start clean and set commit.
   state.SetNeedsBeginMainFrame();
 
   // Make a main frame, commit and activate it. But don't draw it.
-  state.OnBeginImplFrame();
+  state.OnBeginImplFrame(0, 10);
   EXPECT_ACTION_UPDATE_STATE(
       SchedulerStateMachine::ACTION_SEND_BEGIN_MAIN_FRAME);
+  EXPECT_SEQUENCE_NUMBERS(10u, 10u, BeginFrameArgs::kInvalidFrameNumber,
+                          BeginFrameArgs::kInvalidFrameNumber,
+                          BeginFrameArgs::kInvalidFrameNumber);
   state.NotifyBeginMainFrameStarted();
   state.NotifyReadyToCommit();
   EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_COMMIT);
+  EXPECT_SEQUENCE_NUMBERS(10u, 10u, 10u, BeginFrameArgs::kInvalidFrameNumber,
+                          BeginFrameArgs::kInvalidFrameNumber);
   state.NotifyReadyToActivate();
   EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_ACTIVATE_SYNC_TREE);
+  EXPECT_SEQUENCE_NUMBERS(10u, 10u, 10u, 10u,
+                          BeginFrameArgs::kInvalidFrameNumber);
 
   // Try to make a new main frame before drawing, but since we would clobber the
   // active tree, we will not do so.
   state.SetNeedsBeginMainFrame();
-  state.OnBeginImplFrame();
+  state.OnBeginImplFrame(0, 11);
   EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_NONE);
+  EXPECT_SEQUENCE_NUMBERS(11u, 10u, 10u, 10u,
+                          BeginFrameArgs::kInvalidFrameNumber);
 }
 
 TEST(SchedulerStateMachineTest, AbortedMainFrameDoesNotResetPendingTree) {
   SchedulerSettings scheduler_settings;
   scheduler_settings.main_frame_before_activation_enabled = true;
   StateMachine state(scheduler_settings);
   SET_UP_STATE(state);
 
   // Perform a commit so that we have an active tree.
   state.SetNeedsBeginMainFrame();
-  state.OnBeginImplFrame();
+  state.IssueNextBeginImplFrame();
   EXPECT_ACTION_UPDATE_STATE(
       SchedulerStateMachine::ACTION_SEND_BEGIN_MAIN_FRAME);
   EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_NONE);
   state.NotifyBeginMainFrameStarted();
   state.NotifyReadyToCommit();
   EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_COMMIT);
   EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_NONE);
   EXPECT_TRUE(state.has_pending_tree());
   state.OnBeginImplFrameDeadline();
   EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_NONE);
 
   // Ask for another commit but abort it. Verify that we didn't reset pending
   // tree state.
   state.SetNeedsBeginMainFrame();
-  state.OnBeginImplFrame();
+  state.IssueNextBeginImplFrame();
   EXPECT_ACTION_UPDATE_STATE(
       SchedulerStateMachine::ACTION_SEND_BEGIN_MAIN_FRAME);
   EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_NONE);
   EXPECT_TRUE(state.has_pending_tree());
   state.NotifyBeginMainFrameStarted();
   state.BeginMainFrameAborted(CommitEarlyOutReason::FINISHED_NO_UPDATES);
   EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_NONE);
   EXPECT_TRUE(state.has_pending_tree());
   state.OnBeginImplFrameDeadline();
   EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_NONE);
 
   // Ask for another commit that doesn't abort.
   state.SetNeedsBeginMainFrame();
-  state.OnBeginImplFrame();
+  state.IssueNextBeginImplFrame();
   EXPECT_ACTION_UPDATE_STATE(
       SchedulerStateMachine::ACTION_SEND_BEGIN_MAIN_FRAME);
   EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_NONE);
   state.NotifyBeginMainFrameStarted();
   state.NotifyReadyToCommit();
   EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_NONE);
   EXPECT_TRUE(state.has_pending_tree());
 
   // Verify that commit is delayed until the pending tree is activated.
   state.NotifyReadyToActivate();
   EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_ACTIVATE_SYNC_TREE);
   EXPECT_FALSE(state.has_pending_tree());
   EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_COMMIT);
   EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_NONE);
   EXPECT_TRUE(state.has_pending_tree());
 }
 
 TEST(SchedulerStateMachineTest, TestFullCycleWithCommitToActive) {
   SchedulerSettings scheduler_settings;
   scheduler_settings.commit_to_active_tree = true;
   scheduler_settings.main_frame_before_activation_enabled = false;
   StateMachine state(scheduler_settings);
   SET_UP_STATE(state)
 
   // Start clean and set commit.
   state.SetNeedsBeginMainFrame();
 
   // Begin the frame.
-  state.OnBeginImplFrame();
+  state.OnBeginImplFrame(0, 10);
   EXPECT_ACTION_UPDATE_STATE(
       SchedulerStateMachine::ACTION_SEND_BEGIN_MAIN_FRAME);
   EXPECT_MAIN_FRAME_STATE(SchedulerStateMachine::BEGIN_MAIN_FRAME_STATE_SENT);
   EXPECT_FALSE(state.NeedsCommit());
   EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_NONE);
+  EXPECT_SEQUENCE_NUMBERS(10u, 10u, BeginFrameArgs::kInvalidFrameNumber,
+                          BeginFrameArgs::kInvalidFrameNumber,
+                          BeginFrameArgs::kInvalidFrameNumber);
 
   // Tell the scheduler the frame finished.
   state.NotifyBeginMainFrameStarted();
   state.NotifyReadyToCommit();
   EXPECT_MAIN_FRAME_STATE(
       SchedulerStateMachine::BEGIN_MAIN_FRAME_STATE_READY_TO_COMMIT);
   // Commit.
   EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_COMMIT);
+  EXPECT_SEQUENCE_NUMBERS(10u, 10u, 10u, BeginFrameArgs::kInvalidFrameNumber,
+                          BeginFrameArgs::kInvalidFrameNumber);
   // Commit always calls NotifyReadyToActivate in this mode.
   state.NotifyReadyToActivate();
   EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_ACTIVATE_SYNC_TREE);
   EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_NONE);
+  EXPECT_SEQUENCE_NUMBERS(10u, 10u, 10u, 10u,
+                          BeginFrameArgs::kInvalidFrameNumber);
 
   // No draw because we haven't received NotifyReadyToDraw yet.
   state.OnBeginImplFrameDeadline();
   EXPECT_TRUE(state.active_tree_needs_first_draw());
   EXPECT_TRUE(state.needs_redraw());
   EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_NONE);
+  EXPECT_SEQUENCE_NUMBERS(10u, 10u, 10u, 10u,
+                          BeginFrameArgs::kInvalidFrameNumber);
 
   // Can't BeginMainFrame yet since last commit hasn't been drawn yet.
   state.SetNeedsBeginMainFrame();
-  state.OnBeginImplFrame();
+  state.OnBeginImplFrame(0, 11);
   EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_NONE);
+  EXPECT_SEQUENCE_NUMBERS(11u, 10u, 10u, 10u,
+                          BeginFrameArgs::kInvalidFrameNumber);
 
   // Now call ready to draw which will allow the draw to happen and
   // BeginMainFrame to be sent.
   state.NotifyReadyToDraw();
   state.OnBeginImplFrameDeadline();
   EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_DRAW_IF_POSSIBLE);
+  EXPECT_SEQUENCE_NUMBERS(11u, 10u, 10u, 10u, 10u);
   // Submit throttled from this point.
   state.DidSubmitCompositorFrame();
   EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_NONE);
 
   // Can't BeginMainFrame yet since we're submit-frame throttled.
-  state.OnBeginImplFrame();
+  state.OnBeginImplFrame(0, 12);
   EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_NONE);
+  EXPECT_SEQUENCE_NUMBERS(12u, 10u, 10u, 10u, 10u);
 
   // CompositorFrameAck unblocks BeginMainFrame.
   state.DidReceiveCompositorFrameAck();
   EXPECT_ACTION_UPDATE_STATE(
       SchedulerStateMachine::ACTION_SEND_BEGIN_MAIN_FRAME);
+  EXPECT_SEQUENCE_NUMBERS(12u, 12u, 10u, 10u, 10u);
   state.NotifyBeginMainFrameStarted();
   state.NotifyReadyToCommit();
   EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_COMMIT);
+  EXPECT_SEQUENCE_NUMBERS(12u, 12u, 12u, 10u, 10u);
   state.NotifyReadyToActivate();
   EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_ACTIVATE_SYNC_TREE);
   EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_NONE);
+  EXPECT_SEQUENCE_NUMBERS(12u, 12u, 12u, 12u, 10u);
 
   // Draw the newly activated tree.
   state.NotifyReadyToDraw();
   state.OnBeginImplFrameDeadline();
   EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_DRAW_IF_POSSIBLE);
   EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_NONE);
+  EXPECT_SEQUENCE_NUMBERS(12u, 12u, 12u, 12u, 12u);
 }
 
 TEST(SchedulerStateMachineTest, TestFullCycleWithCommitRequestInbetween) {
   SchedulerSettings default_scheduler_settings;
   StateMachine state(default_scheduler_settings);
   SET_UP_STATE(state)
 
   // Start clean and set commit.
   state.SetNeedsBeginMainFrame();
 
   // Begin the frame.
-  state.OnBeginImplFrame();
+  state.IssueNextBeginImplFrame();
   EXPECT_ACTION_UPDATE_STATE(
       SchedulerStateMachine::ACTION_SEND_BEGIN_MAIN_FRAME);
   EXPECT_MAIN_FRAME_STATE(SchedulerStateMachine::BEGIN_MAIN_FRAME_STATE_SENT);
   EXPECT_FALSE(state.NeedsCommit());
   EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_NONE);
 
   // Request another commit while the commit is in flight.
   state.SetNeedsBeginMainFrame();
   EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_NONE);
 
@@ skipping 18 matching lines @@
   EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_DRAW_IF_POSSIBLE);
   state.DidSubmitCompositorFrame();
   state.DidReceiveCompositorFrameAck();
 
   // Should be synchronized, no draw needed, no action needed.
   EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_NONE);
   EXPECT_MAIN_FRAME_STATE(SchedulerStateMachine::BEGIN_MAIN_FRAME_STATE_IDLE);
   EXPECT_FALSE(state.needs_redraw());
 
   // Next BeginImplFrame should initiate second commit.
-  state.OnBeginImplFrame();
+  state.IssueNextBeginImplFrame();
   EXPECT_ACTION_UPDATE_STATE(
       SchedulerStateMachine::ACTION_SEND_BEGIN_MAIN_FRAME);
 }
 
 TEST(SchedulerStateMachineTest, TestNoRequestCommitWhenInvisible) {
   SchedulerSettings default_scheduler_settings;
   StateMachine state(default_scheduler_settings);
   state.SetVisible(true);
   EXPECT_ACTION_UPDATE_STATE(
       SchedulerStateMachine::ACTION_BEGIN_COMPOSITOR_FRAME_SINK_CREATION);
@@ skipping 42 matching lines @@
 // "EarlyOut_CompositorFrameSinkLost" cases.
 TEST(SchedulerStateMachineTest, TestAbortBeginMainFrameBecauseInvisible) {
   SchedulerSettings default_scheduler_settings;
   StateMachine state(default_scheduler_settings);
   SET_UP_STATE(state)
 
   // Start clean and set commit.
   state.SetNeedsBeginMainFrame();
 
   // Begin the frame while visible.
-  state.OnBeginImplFrame();
+  state.IssueNextBeginImplFrame();
   EXPECT_ACTION_UPDATE_STATE(
       SchedulerStateMachine::ACTION_SEND_BEGIN_MAIN_FRAME);
   EXPECT_MAIN_FRAME_STATE(SchedulerStateMachine::BEGIN_MAIN_FRAME_STATE_SENT);
   EXPECT_FALSE(state.NeedsCommit());
   EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_NONE);
 
   // Become invisible and abort BeginMainFrame.
   state.SetVisible(false);
   state.NotifyBeginMainFrameStarted();
   state.BeginMainFrameAborted(CommitEarlyOutReason::ABORTED_NOT_VISIBLE);
@@ skipping 13 matching lines @@
   // Become visible again.
   state.SetVisible(true);
 
   // Although we have aborted on this frame and haven't cancelled the commit
   // (i.e. need another), don't send another BeginMainFrame yet.
   EXPECT_MAIN_FRAME_STATE(SchedulerStateMachine::BEGIN_MAIN_FRAME_STATE_IDLE);
   EXPECT_ACTION(SchedulerStateMachine::ACTION_NONE);
   EXPECT_TRUE(state.NeedsCommit());
 
   // Start a new frame.
-  state.OnBeginImplFrame();
+  state.IssueNextBeginImplFrame();
   EXPECT_ACTION_UPDATE_STATE(
       SchedulerStateMachine::ACTION_SEND_BEGIN_MAIN_FRAME);
 
   // We should be starting the commit now.
   EXPECT_MAIN_FRAME_STATE(SchedulerStateMachine::BEGIN_MAIN_FRAME_STATE_SENT);
   EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_NONE);
 }
 
 // See ProxyMain::BeginMainFrame "EarlyOut_NoUpdates" case.
 TEST(SchedulerStateMachineTest, TestAbortBeginMainFrameBecauseCommitNotNeeded) {
   SchedulerSettings default_scheduler_settings;
   StateMachine state(default_scheduler_settings);
   state.SetVisible(true);
   EXPECT_ACTION_UPDATE_STATE(
       SchedulerStateMachine::ACTION_BEGIN_COMPOSITOR_FRAME_SINK_CREATION);
   EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_NONE);
   state.DidCreateAndInitializeCompositorFrameSink();
   state.SetCanDraw(true);
 
   // Get into a begin frame / commit state.
   state.SetNeedsBeginMainFrame();
-  state.OnBeginImplFrame();
+  state.IssueNextBeginImplFrame();
   EXPECT_ACTION_UPDATE_STATE(
       SchedulerStateMachine::ACTION_SEND_BEGIN_MAIN_FRAME);
   EXPECT_MAIN_FRAME_STATE(SchedulerStateMachine::BEGIN_MAIN_FRAME_STATE_SENT);
   EXPECT_FALSE(state.NeedsCommit());
   EXPECT_ACTION(SchedulerStateMachine::ACTION_NONE);
 
   // Abort the commit, true means that the BeginMainFrame was sent but there
   // was no work to do on the main thread.
   state.NotifyBeginMainFrameStarted();
   state.BeginMainFrameAborted(CommitEarlyOutReason::FINISHED_NO_UPDATES);
 
   // NeedsCommit should now be false because the commit was actually handled.
   EXPECT_FALSE(state.NeedsCommit());
 
   // Since the commit was aborted, we don't need to try and draw.
   EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_NONE);
   state.OnBeginImplFrameDeadline();
   EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_NONE);
 
   // Verify another commit doesn't start on another frame either.
   EXPECT_FALSE(state.NeedsCommit());
   EXPECT_MAIN_FRAME_STATE(SchedulerStateMachine::BEGIN_MAIN_FRAME_STATE_IDLE);
 
-  state.OnBeginImplFrame();
+  state.IssueNextBeginImplFrame();
   EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_NONE);
   state.OnBeginImplFrameDeadline();
   EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_NONE);
 
   // Verify another commit can start if requested, though.
   state.SetNeedsBeginMainFrame();
   EXPECT_MAIN_FRAME_STATE(SchedulerStateMachine::BEGIN_MAIN_FRAME_STATE_IDLE);
-  state.OnBeginImplFrame();
+  state.IssueNextBeginImplFrame();
   EXPECT_ACTION(SchedulerStateMachine::ACTION_SEND_BEGIN_MAIN_FRAME);
 }
 
 TEST(SchedulerStateMachineTest, TestFirstContextCreation) {
   SchedulerSettings default_scheduler_settings;
   StateMachine state(default_scheduler_settings);
   state.SetVisible(true);
   state.SetCanDraw(true);
 
   EXPECT_ACTION_UPDATE_STATE(
       SchedulerStateMachine::ACTION_BEGIN_COMPOSITOR_FRAME_SINK_CREATION);
   state.CreateAndInitializeCompositorFrameSinkWithActivatedCommit();
   EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_NONE);
 
   // Check that the first init does not SetNeedsBeginMainFrame.
-  state.OnBeginImplFrame();
+  state.IssueNextBeginImplFrame();
   EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_NONE);
   state.OnBeginImplFrameDeadline();
   EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_NONE);
 
   // Check that a needs commit initiates a BeginMainFrame.
   state.SetNeedsBeginMainFrame();
-  state.OnBeginImplFrame();
+  state.IssueNextBeginImplFrame();
   EXPECT_ACTION_UPDATE_STATE(
       SchedulerStateMachine::ACTION_SEND_BEGIN_MAIN_FRAME);
 }
 
 TEST(SchedulerStateMachineTest, TestContextLostWhenCompletelyIdle) {
   SchedulerSettings default_scheduler_settings;
   StateMachine state(default_scheduler_settings);
   SET_UP_STATE(state)
 
   EXPECT_NE(SchedulerStateMachine::ACTION_BEGIN_COMPOSITOR_FRAME_SINK_CREATION,
             state.NextAction());
   state.DidLoseCompositorFrameSink();
 
   EXPECT_ACTION_UPDATE_STATE(
       SchedulerStateMachine::ACTION_BEGIN_COMPOSITOR_FRAME_SINK_CREATION);
   EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_NONE);
 
   // Once context recreation begins, nothing should happen.
   EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_NONE);
 
   // Recreate the context.
   state.CreateAndInitializeCompositorFrameSinkWithActivatedCommit();
 
   // When the context is recreated, we should begin a commit.
-  state.OnBeginImplFrame();
+  state.IssueNextBeginImplFrame();
   EXPECT_ACTION_UPDATE_STATE(
       SchedulerStateMachine::ACTION_SEND_BEGIN_MAIN_FRAME);
 }
 
 TEST(SchedulerStateMachineTest,
      TestContextLostWhenIdleAndCommitRequestedWhileRecreating) {
   SchedulerSettings default_scheduler_settings;
   StateMachine state(default_scheduler_settings);
   SET_UP_STATE(state)
 
   EXPECT_NE(SchedulerStateMachine::ACTION_BEGIN_COMPOSITOR_FRAME_SINK_CREATION,
             state.NextAction());
   state.DidLoseCompositorFrameSink();
   EXPECT_EQ(state.compositor_frame_sink_state(),
             SchedulerStateMachine::COMPOSITOR_FRAME_SINK_NONE);
 
   EXPECT_ACTION_UPDATE_STATE(
       SchedulerStateMachine::ACTION_BEGIN_COMPOSITOR_FRAME_SINK_CREATION);
   EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_NONE);
 
   // Once context recreation begins, nothing should happen.
-  state.OnBeginImplFrame();
+  state.IssueNextBeginImplFrame();
   EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_NONE);
   state.OnBeginImplFrameDeadline();
   EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_NONE);
 
   // While context is recreating, commits shouldn't begin.
   state.SetNeedsBeginMainFrame();
-  state.OnBeginImplFrame();
+  state.IssueNextBeginImplFrame();
   EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_NONE);
   state.OnBeginImplFrameDeadline();
   EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_NONE);
 
   // Recreate the context
   state.DidCreateAndInitializeCompositorFrameSink();
   EXPECT_EQ(
       state.compositor_frame_sink_state(),
       SchedulerStateMachine::COMPOSITOR_FRAME_SINK_WAITING_FOR_FIRST_COMMIT);
   EXPECT_FALSE(state.RedrawPending());
 
   // When the context is recreated, we wait until the next BeginImplFrame
   // before starting.
   EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_NONE);
 
   // When the BeginFrame comes in we should begin a commit
-  state.OnBeginImplFrame();
+  state.IssueNextBeginImplFrame();
   EXPECT_ACTION_UPDATE_STATE(
       SchedulerStateMachine::ACTION_SEND_BEGIN_MAIN_FRAME);
   EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_NONE);
   EXPECT_MAIN_FRAME_STATE(SchedulerStateMachine::BEGIN_MAIN_FRAME_STATE_SENT);
 
   // Until that commit finishes, we shouldn't be drawing.
   state.OnBeginImplFrameDeadline();
   EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_NONE);
 
   // Finish the commit, which should make the surface active.
   state.NotifyBeginMainFrameStarted();
   state.NotifyReadyToCommit();
   EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_COMMIT);
   EXPECT_EQ(state.compositor_frame_sink_state(),
             SchedulerStateMachine::
                 COMPOSITOR_FRAME_SINK_WAITING_FOR_FIRST_ACTIVATION);
   state.NotifyReadyToActivate();
   EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_ACTIVATE_SYNC_TREE);
   EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_NONE);
   EXPECT_EQ(state.compositor_frame_sink_state(),
             SchedulerStateMachine::COMPOSITOR_FRAME_SINK_ACTIVE);
 
   // Finishing the first commit after initializing an CompositorFrameSink should
   // automatically cause a redraw.
   EXPECT_TRUE(state.RedrawPending());
-  state.OnBeginImplFrame();
+  state.IssueNextBeginImplFrame();
   EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_NONE);
   state.OnBeginImplFrameDeadline();
   EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_DRAW_IF_POSSIBLE);
   EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_NONE);
   EXPECT_FALSE(state.RedrawPending());
 
   // Next frame as no work to do.
-  state.OnBeginImplFrame();
+  state.IssueNextBeginImplFrame();
   EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_NONE);
   state.OnBeginImplFrameDeadline();
   EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_NONE);
 
   // Once the context is recreated, whether we draw should be based on
   // SetCanDraw if waiting on first draw after activate.
   state.SetNeedsRedraw(true);
-  state.OnBeginImplFrame();
+  state.IssueNextBeginImplFrame();
   EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_NONE);
   state.OnBeginImplFrameDeadline();
   EXPECT_ACTION(SchedulerStateMachine::ACTION_DRAW_IF_POSSIBLE);
   state.SetCanDraw(false);
   EXPECT_ACTION(SchedulerStateMachine::ACTION_NONE);
   state.SetCanDraw(true);
   EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_DRAW_IF_POSSIBLE);
   EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_NONE);
 
   // Once the context is recreated, whether we draw should be based on
   // SetCanDraw if waiting on first draw after activate.
   state.SetNeedsRedraw(true);
   state.SetNeedsBeginMainFrame();
-  state.OnBeginImplFrame();
+  state.IssueNextBeginImplFrame();
   EXPECT_ACTION_UPDATE_STATE(
       SchedulerStateMachine::ACTION_SEND_BEGIN_MAIN_FRAME);
   EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_NONE);
   // Activate so we need the first draw
   state.NotifyBeginMainFrameStarted();
   state.NotifyReadyToCommit();
   EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_COMMIT);
   state.NotifyReadyToActivate();
   EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_ACTIVATE_SYNC_TREE);
   EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_NONE);
@@ skipping 11 matching lines @@
 TEST(SchedulerStateMachineTest, TestContextLostWhileCommitInProgress) {
   SchedulerSettings scheduler_settings;
   StateMachine state(scheduler_settings);
   SET_UP_STATE(state)
 
   // Get a commit in flight.
   state.SetNeedsBeginMainFrame();
 
   // Set damage and expect a draw.
   state.SetNeedsRedraw(true);
-  state.OnBeginImplFrame();
+  state.OnBeginImplFrame(0, 10);
   EXPECT_ACTION_UPDATE_STATE(
       SchedulerStateMachine::ACTION_SEND_BEGIN_MAIN_FRAME);
   EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_NONE);
   state.OnBeginImplFrameDeadline();
   EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_DRAW_IF_POSSIBLE);
   state.DidSubmitCompositorFrame();
   state.DidReceiveCompositorFrameAck();
   EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_NONE);
+  EXPECT_SEQUENCE_NUMBERS(10u, 10u, BeginFrameArgs::kInvalidFrameNumber,
+                          BeginFrameArgs::kInvalidFrameNumber,
+                          BeginFrameArgs::kInvalidFrameNumber);
 
   // Cause a lost context while the BeginMainFrame is in flight.
   state.DidLoseCompositorFrameSink();
+  EXPECT_FALSE(state.BeginFrameNeeded());
 
   // Ask for another draw. Expect nothing happens.
   state.SetNeedsRedraw(true);
   EXPECT_ACTION(SchedulerStateMachine::ACTION_NONE);
 
   // Finish the frame, commit and activate.
   state.NotifyBeginMainFrameStarted();
   state.NotifyReadyToCommit();
   EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_COMMIT);
+  EXPECT_SEQUENCE_NUMBERS(10u, 10u, 10u, BeginFrameArgs::kInvalidFrameNumber,
+                          BeginFrameArgs::kInvalidFrameNumber);
   state.NotifyReadyToActivate();
   EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_ACTIVATE_SYNC_TREE);
+  EXPECT_SEQUENCE_NUMBERS(10u, 10u, 10u, 10u,
+                          BeginFrameArgs::kInvalidFrameNumber);
 
   // We will abort the draw when the CompositorFrameSink is lost if we are
   // waiting for the first draw to unblock the main thread.
   EXPECT_TRUE(state.active_tree_needs_first_draw());
   EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_DRAW_ABORT);
+  EXPECT_SEQUENCE_NUMBERS(10u, 10u, 10u, 10u,
+                          BeginFrameArgs::kInvalidFrameNumber);
 
   // Expect to begin context recreation only in BEGIN_IMPL_FRAME_STATE_IDLE
   EXPECT_IMPL_FRAME_STATE(SchedulerStateMachine::BEGIN_IMPL_FRAME_STATE_IDLE);
   EXPECT_ACTION(
       SchedulerStateMachine::ACTION_BEGIN_COMPOSITOR_FRAME_SINK_CREATION);
 
-  state.OnBeginImplFrame();
+  state.OnBeginImplFrame(0, 11);
   EXPECT_IMPL_FRAME_STATE(
       SchedulerStateMachine::BEGIN_IMPL_FRAME_STATE_INSIDE_BEGIN_FRAME);
   EXPECT_ACTION(SchedulerStateMachine::ACTION_NONE);
+  EXPECT_SEQUENCE_NUMBERS(11u, 10u, 10u, 10u,
+                          BeginFrameArgs::kInvalidFrameNumber);
 
   state.OnBeginImplFrameDeadline();
   EXPECT_IMPL_FRAME_STATE(
       SchedulerStateMachine::BEGIN_IMPL_FRAME_STATE_INSIDE_DEADLINE);
   EXPECT_ACTION(SchedulerStateMachine::ACTION_NONE);
+  EXPECT_SEQUENCE_NUMBERS(11u, 10u, 10u, 11u, 11u);
 }
 
 TEST(SchedulerStateMachineTest,
      TestContextLostWhileCommitInProgressAndAnotherCommitRequested) {
   SchedulerSettings scheduler_settings;
   StateMachine state(scheduler_settings);
   SET_UP_STATE(state)
 
   // Get a commit in flight.
   state.SetNeedsBeginMainFrame();
   EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_NONE);
 
   // Set damage and expect a draw.
   state.SetNeedsRedraw(true);
-  state.OnBeginImplFrame();
+  state.IssueNextBeginImplFrame();
   EXPECT_ACTION_UPDATE_STATE(
       SchedulerStateMachine::ACTION_SEND_BEGIN_MAIN_FRAME);
   EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_NONE);
   state.OnBeginImplFrameDeadline();
   EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_DRAW_IF_POSSIBLE);
   state.DidSubmitCompositorFrame();
   state.DidReceiveCompositorFrameAck();
   EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_NONE);
 
   // Cause a lost context while the BeginMainFrame is in flight.
@@ skipping 13 matching lines @@
   EXPECT_TRUE(state.active_tree_needs_first_draw());
 
   // Because the CompositorFrameSink is missing, we expect the draw to abort.
   EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_DRAW_ABORT);
 
   // Expect to begin context recreation only in BEGIN_IMPL_FRAME_STATE_IDLE
   EXPECT_IMPL_FRAME_STATE(SchedulerStateMachine::BEGIN_IMPL_FRAME_STATE_IDLE);
   EXPECT_ACTION(
       SchedulerStateMachine::ACTION_BEGIN_COMPOSITOR_FRAME_SINK_CREATION);
 
-  state.OnBeginImplFrame();
+  state.IssueNextBeginImplFrame();
   EXPECT_IMPL_FRAME_STATE(
       SchedulerStateMachine::BEGIN_IMPL_FRAME_STATE_INSIDE_BEGIN_FRAME);
   EXPECT_ACTION(SchedulerStateMachine::ACTION_NONE);
 
   state.OnBeginImplFrameDeadline();
   EXPECT_IMPL_FRAME_STATE(
       SchedulerStateMachine::BEGIN_IMPL_FRAME_STATE_INSIDE_DEADLINE);
   EXPECT_ACTION(SchedulerStateMachine::ACTION_NONE);
 
   state.OnBeginImplFrameIdle();
   EXPECT_ACTION_UPDATE_STATE(
       SchedulerStateMachine::ACTION_BEGIN_COMPOSITOR_FRAME_SINK_CREATION);
 
   // After we get a new CompositorFrameSink, the commit flow should start.
   state.CreateAndInitializeCompositorFrameSinkWithActivatedCommit();
-  state.OnBeginImplFrame();
+  state.IssueNextBeginImplFrame();
   EXPECT_ACTION_UPDATE_STATE(
       SchedulerStateMachine::ACTION_SEND_BEGIN_MAIN_FRAME);
   EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_NONE);
   state.NotifyBeginMainFrameStarted();
   state.NotifyReadyToCommit();
   EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_COMMIT);
   EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_NONE);
   state.NotifyReadyToActivate();
   EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_ACTIVATE_SYNC_TREE);
   EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_NONE);
@@ skipping 13 matching lines @@
   state.SetNeedsRedraw(true);
 
   // Cause a lost CompositorFrameSink, and restore it.
   state.DidLoseCompositorFrameSink();
   EXPECT_ACTION_UPDATE_STATE(
       SchedulerStateMachine::ACTION_BEGIN_COMPOSITOR_FRAME_SINK_CREATION);
   EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_NONE);
   state.DidCreateAndInitializeCompositorFrameSink();
 
   EXPECT_FALSE(state.RedrawPending());
-  state.OnBeginImplFrame();
+  state.IssueNextBeginImplFrame();
   EXPECT_ACTION(SchedulerStateMachine::ACTION_SEND_BEGIN_MAIN_FRAME);
 }
 
 TEST(SchedulerStateMachineTest,
      TestPendingActivationsShouldBeForcedAfterLostCompositorFrameSink) {
   SchedulerSettings default_scheduler_settings;
   StateMachine state(default_scheduler_settings);
   SET_UP_STATE(state)
 
   state.SetBeginMainFrameState(
@@ skipping 42 matching lines @@
   EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_NONE);
   state.CreateAndInitializeCompositorFrameSinkWithActivatedCommit();
   state.SetVisible(false);
   state.SetNeedsBeginMainFrame();
   EXPECT_ACTION(SchedulerStateMachine::ACTION_NONE);
   EXPECT_FALSE(state.BeginFrameNeeded());
 
   // When become visible again, the needs commit should still be pending.
   state.SetVisible(true);
   EXPECT_TRUE(state.BeginFrameNeeded());
-  state.OnBeginImplFrame();
+  state.IssueNextBeginImplFrame();
   EXPECT_ACTION_UPDATE_STATE(
       SchedulerStateMachine::ACTION_SEND_BEGIN_MAIN_FRAME);
 }
 
 TEST(SchedulerStateMachineTest, TestFinishCommitWhenCommitInProgress) {
   SchedulerSettings default_scheduler_settings;
   StateMachine state(default_scheduler_settings);
   state.SetVisible(true);
   EXPECT_ACTION_UPDATE_STATE(
       SchedulerStateMachine::ACTION_BEGIN_COMPOSITOR_FRAME_SINK_CREATION);
@@ skipping 143 matching lines @@
 }
 
 TEST(SchedulerStateMachineTest,
      TestTriggerDeadlineImmediatelyAfterAbortedCommit) {
   SchedulerSettings default_scheduler_settings;
   StateMachine state(default_scheduler_settings);
   SET_UP_STATE(state)
 
   // This test mirrors what happens during the first frame of a scroll gesture.
   // First we get the input event and a BeginFrame.
-  state.OnBeginImplFrame();
+  state.IssueNextBeginImplFrame();
 
   // As a response the compositor requests a redraw and a commit to tell the
   // main thread about the new scroll offset.
   state.SetNeedsRedraw(true);
   state.SetNeedsBeginMainFrame();
 
   // We should start the commit normally.
   EXPECT_ACTION_UPDATE_STATE(
       SchedulerStateMachine::ACTION_SEND_BEGIN_MAIN_FRAME);
   EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_NONE);
@@ skipping 14 matching lines @@
   StateMachine& state = *state_ptr;
 
   state.NotifyBeginMainFrameStarted();
   state.NotifyReadyToCommit();
   EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_COMMIT);
   EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_NONE);
   state.NotifyReadyToActivate();
   EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_ACTIVATE_SYNC_TREE);
   EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_NONE);
 
-  state.OnBeginImplFrame();
+  state.IssueNextBeginImplFrame();
   EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_NONE);
 
   EXPECT_TRUE(state.ShouldTriggerBeginImplFrameDeadlineImmediately());
   state.OnBeginImplFrameDeadline();
   EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_DRAW_IF_POSSIBLE);
   state.DidSubmitCompositorFrame();
 }
 
 TEST(SchedulerStateMachineTest, TestImplLatencyTakesPriority) {
   SchedulerSettings default_scheduler_settings;
   StateMachine state(default_scheduler_settings);
   SET_UP_STATE(state)
 
   // This test ensures that impl-draws are prioritized over main thread updates
   // in prefer impl latency mode.
   state.SetNeedsRedraw(true);
   state.SetNeedsBeginMainFrame();
-  state.OnBeginImplFrame();
+  state.IssueNextBeginImplFrame();
   EXPECT_ACTION_UPDATE_STATE(
       SchedulerStateMachine::ACTION_SEND_BEGIN_MAIN_FRAME);
   EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_NONE);
 
   // Verify the deadline is not triggered early until we enter
   // prefer impl latency mode.
   EXPECT_FALSE(state.ShouldTriggerBeginImplFrameDeadlineImmediately());
   state.SetTreePrioritiesAndScrollState(
       SMOOTHNESS_TAKES_PRIORITY,
       ScrollHandlerState::SCROLL_DOES_NOT_AFFECT_SCROLL_HANDLER);
@@ skipping 16 matching lines @@
   EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_NONE);
 
   // Finish the previous commit and draw it.
   FinishPreviousCommitAndDrawWithoutExitingDeadline(&state);
   EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_NONE);
 
   // Verify we do not send another BeginMainFrame if was are submit-frame
   // throttled and did not just submit one.
   state.SetNeedsBeginMainFrame();
   EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_NONE);
-  state.OnBeginImplFrame();
+  state.IssueNextBeginImplFrame();
   EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_NONE);
   EXPECT_FALSE(state.ShouldTriggerBeginImplFrameDeadlineImmediately());
   state.OnBeginImplFrameDeadline();
   EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_NONE);
 }
 
 TEST(SchedulerStateMachineTest,
      TestTriggerDeadlineImmediatelyOnLostCompositorFrameSink) {
   SchedulerSettings default_scheduler_settings;
   StateMachine state(default_scheduler_settings);
   SET_UP_STATE(state)
 
   state.SetNeedsBeginMainFrame();
 
-  state.OnBeginImplFrame();
+  state.IssueNextBeginImplFrame();
   EXPECT_ACTION_UPDATE_STATE(
       SchedulerStateMachine::ACTION_SEND_BEGIN_MAIN_FRAME);
   EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_NONE);
   EXPECT_FALSE(state.ShouldTriggerBeginImplFrameDeadlineImmediately());
 
   state.DidLoseCompositorFrameSink();
   EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_NONE);
   // The deadline should be triggered immediately when CompositorFrameSink is
   // lost.
   EXPECT_TRUE(state.ShouldTriggerBeginImplFrameDeadlineImmediately());
 }
 
 TEST(SchedulerStateMachineTest, TestTriggerDeadlineImmediatelyWhenInvisible) {
   SchedulerSettings default_scheduler_settings;
   StateMachine state(default_scheduler_settings);
   SET_UP_STATE(state)
 
   state.SetNeedsBeginMainFrame();
 
-  state.OnBeginImplFrame();
+  state.IssueNextBeginImplFrame();
   EXPECT_ACTION_UPDATE_STATE(
       SchedulerStateMachine::ACTION_SEND_BEGIN_MAIN_FRAME);
   EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_NONE);
   EXPECT_FALSE(state.ShouldTriggerBeginImplFrameDeadlineImmediately());
 
   state.SetVisible(false);
   EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_NONE);
   EXPECT_TRUE(state.PendingActivationsShouldBeForced());
   EXPECT_TRUE(state.ShouldTriggerBeginImplFrameDeadlineImmediately());
 }
 
 TEST(SchedulerStateMachineTest,
      TestTriggerDeadlineImmediatelyWhenBeginFrameSourcePaused) {
   SchedulerSettings default_scheduler_settings;
   StateMachine state(default_scheduler_settings);
   SET_UP_STATE(state)
 
   state.SetNeedsBeginMainFrame();
 
-  state.OnBeginImplFrame();
+  state.IssueNextBeginImplFrame();
   EXPECT_ACTION_UPDATE_STATE(
       SchedulerStateMachine::ACTION_SEND_BEGIN_MAIN_FRAME);
   EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_NONE);
   EXPECT_FALSE(state.ShouldTriggerBeginImplFrameDeadlineImmediately());
 
   state.SetBeginFrameSourcePaused(true);
   EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_NONE);
   EXPECT_TRUE(state.PendingActivationsShouldBeForced());
   EXPECT_TRUE(state.ShouldTriggerBeginImplFrameDeadlineImmediately());
 }
 
 TEST(SchedulerStateMachineTest, TestDeferCommit) {
   SchedulerSettings settings;
   StateMachine state(settings);
   SET_UP_STATE(state)
 
   state.SetDeferCommits(true);
 
   state.SetNeedsBeginMainFrame();
   EXPECT_FALSE(state.BeginFrameNeeded());
   EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_NONE);
 
-  state.OnBeginImplFrame();
+  state.IssueNextBeginImplFrame();
   EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_NONE);
 
   state.OnBeginImplFrameDeadline();
   EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_NONE);
 
   state.SetDeferCommits(false);
-  state.OnBeginImplFrame();
+  state.IssueNextBeginImplFrame();
   EXPECT_ACTION_UPDATE_STATE(
       SchedulerStateMachine::ACTION_SEND_BEGIN_MAIN_FRAME);
 }
 
 TEST(SchedulerStateMachineTest, EarlyOutCommitWantsProactiveBeginFrame) {
   SchedulerSettings settings;
   StateMachine state(settings);
   SET_UP_STATE(state);
 
   EXPECT_FALSE(state.ProactiveBeginFrameWanted());
   bool commit_has_no_updates = true;
   state.WillCommit(commit_has_no_updates);
   EXPECT_TRUE(state.ProactiveBeginFrameWanted());
-  state.OnBeginImplFrame();
+  state.IssueNextBeginImplFrame();
   EXPECT_FALSE(state.ProactiveBeginFrameWanted());
 }
 
 TEST(SchedulerStateMachineTest,
      NoCompositorFrameSinkCreationWhileCommitPending) {
   SchedulerSettings settings;
   StateMachine state(settings);
   SET_UP_STATE(state);
 
   // Set up the request for a commit and start a frame.
   state.SetNeedsBeginMainFrame();
-  state.OnBeginImplFrame();
+  state.IssueNextBeginImplFrame();
   PerformAction(&state, SchedulerStateMachine::ACTION_SEND_BEGIN_MAIN_FRAME);
 
   // Lose the CompositorFrameSink.
   state.DidLoseCompositorFrameSink();
 
   // The scheduler shouldn't trigger the CompositorFrameSink creation till the
   // previous commit has been cleared.
   EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_NONE);
 
   // Trigger the deadline and ensure that the scheduler does not trigger any
   // actions until we receive a response for the pending commit.
   state.OnBeginImplFrameDeadline();
   state.OnBeginImplFrameIdle();
   EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_NONE);
 
   // Abort the commit, since that is what we expect the main thread to do if the
   // CompositorFrameSink was lost due to a synchronous call from the main thread
   // to release the CompositorFrameSink.
   state.NotifyBeginMainFrameStarted();
   state.BeginMainFrameAborted(
       CommitEarlyOutReason::ABORTED_COMPOSITOR_FRAME_SINK_LOST);
 
   // The scheduler should begin the CompositorFrameSink creation now.
   EXPECT_ACTION_UPDATE_STATE(
       SchedulerStateMachine::ACTION_BEGIN_COMPOSITOR_FRAME_SINK_CREATION);
 }
 
+TEST(SchedulerStateMachineTest, TestBeginFrameFreshnessInitialState) {
+  SchedulerSettings default_scheduler_settings;
+  StateMachine state(default_scheduler_settings);
+  SET_UP_STATE(state)
+
+  // Initially, we report invalid frame numbers.
+  EXPECT_SEQUENCE_NUMBERS(
+      BeginFrameArgs::kInvalidFrameNumber, BeginFrameArgs::kInvalidFrameNumber,
+      BeginFrameArgs::kInvalidFrameNumber, BeginFrameArgs::kInvalidFrameNumber,
+      BeginFrameArgs::kInvalidFrameNumber);
+}
+
+TEST(SchedulerStateMachineTest, TestBeginFrameFreshnessWithoutUpdates) {
+  // Setup without any requested updates.
+  SchedulerSettings default_scheduler_settings;
+  StateMachine state(default_scheduler_settings);
+  SET_UP_STATE(state)
+  state.SetNeedsRedraw(false);
+  EXPECT_FALSE(state.RedrawPending());
+  EXPECT_FALSE(state.NeedsCommit());
+
+  // OnBeginImplFrame() updates the sequence number.
+  state.OnBeginImplFrame(0, 10);
+  EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_NONE);
+  EXPECT_SEQUENCE_NUMBERS(10u, BeginFrameArgs::kInvalidFrameNumber,
+                          BeginFrameArgs::kInvalidFrameNumber,
+                          BeginFrameArgs::kInvalidFrameNumber,
+                          BeginFrameArgs::kInvalidFrameNumber);
+
+  // When no updates are required, OnBeginImplFrameDeadline() updates active
+  // tree and compositor frame freshness.
+  state.OnBeginImplFrameDeadline();
+  EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_NONE);
+  EXPECT_SEQUENCE_NUMBERS(10u, BeginFrameArgs::kInvalidFrameNumber,
+                          BeginFrameArgs::kInvalidFrameNumber, 10u, 10u);
+  state.OnBeginImplFrameIdle();
+  EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_NONE);
+}
+
+TEST(SchedulerStateMachineTest, TestBeginFrameFreshnessWithImplFrameUpdates) {
+  // Setup with an impl-thread draw requested.
+  SchedulerSettings default_scheduler_settings;
+  StateMachine state(default_scheduler_settings);
+  SET_UP_STATE(state)
+  state.SetNeedsRedraw(true);
+  EXPECT_TRUE(state.RedrawPending());
+  EXPECT_FALSE(state.NeedsCommit());
+
+  // OnBeginImplFrame() updates the sequence number.
+  state.OnBeginImplFrame(0, 10);
+  EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_NONE);
+  EXPECT_SEQUENCE_NUMBERS(10u, BeginFrameArgs::kInvalidFrameNumber,
+                          BeginFrameArgs::kInvalidFrameNumber,
+                          BeginFrameArgs::kInvalidFrameNumber,
+                          BeginFrameArgs::kInvalidFrameNumber);
+
+  // With only an impl-thread draw requested, OnBeginImplFrameDeadline()
+  // updates the active tree freshness.
+  state.OnBeginImplFrameDeadline();
+  EXPECT_SEQUENCE_NUMBERS(10u, BeginFrameArgs::kInvalidFrameNumber,
+                          BeginFrameArgs::kInvalidFrameNumber, 10u,
+                          BeginFrameArgs::kInvalidFrameNumber);
+
+  // Compositor frame freshness is updated when active tree is drawn.
+  EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_DRAW_IF_POSSIBLE);
+  EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_NONE);
+  EXPECT_FALSE(state.RedrawPending());
+  state.DidSubmitCompositorFrame();
+  state.DidReceiveCompositorFrameAck();
+  EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_NONE);
+  EXPECT_SEQUENCE_NUMBERS(10u, BeginFrameArgs::kInvalidFrameNumber,
+                          BeginFrameArgs::kInvalidFrameNumber, 10u, 10u);
+  state.OnBeginImplFrameIdle();
+  EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_NONE);
+}
+
+TEST(SchedulerStateMachineTest, TestBeginFrameFreshnessWithMainFrameUpdates) {
+  // Setup with a BeginMainFrame requested.
+  SchedulerSettings default_scheduler_settings;
+  StateMachine state(default_scheduler_settings);
+  SET_UP_STATE(state)
+  state.SetNeedsRedraw(false);
+  state.SetNeedsBeginMainFrameForTest(true);
+  EXPECT_FALSE(state.RedrawPending());
+  EXPECT_TRUE(state.NeedsCommit());
+
+  // OnBeginImplFrame() updates the sequence number, WillSendBeginMainFrame()
+  // updates begin_main_frame_sent sequence number.
+  state.OnBeginImplFrame(0, 10);
+  EXPECT_ACTION_UPDATE_STATE(
+      SchedulerStateMachine::ACTION_SEND_BEGIN_MAIN_FRAME);
+  EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_NONE);
+  EXPECT_FALSE(state.NeedsCommit());
+  EXPECT_TRUE(state.CommitPending());
+  EXPECT_SEQUENCE_NUMBERS(10u, 10u, BeginFrameArgs::kInvalidFrameNumber,
+                          BeginFrameArgs::kInvalidFrameNumber,
+                          BeginFrameArgs::kInvalidFrameNumber);
+
+  // When a BeginMainFrame is needed, OnBeginImplFrameDeadline() updates no
+  // freshness numbers.
+  state.OnBeginImplFrameDeadline();
+  EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_NONE);
+  EXPECT_SEQUENCE_NUMBERS(10u, 10u, BeginFrameArgs::kInvalidFrameNumber,
+                          BeginFrameArgs::kInvalidFrameNumber,
+                          BeginFrameArgs::kInvalidFrameNumber);
+  state.OnBeginImplFrameIdle();
+  EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_NONE);
+
+  // When a main frame is in progress, OnBeginImplFrameDeadline() updates no
+  // freshness numbers.
+  state.NotifyBeginMainFrameStarted();
+  state.OnBeginImplFrame(0, 11);
+  EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_NONE);
+  state.OnBeginImplFrameDeadline();
+  EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_NONE);
+  EXPECT_SEQUENCE_NUMBERS(11u, 10u, BeginFrameArgs::kInvalidFrameNumber,
+                          BeginFrameArgs::kInvalidFrameNumber,
+                          BeginFrameArgs::kInvalidFrameNumber);
+  state.OnBeginImplFrameIdle();
+  EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_NONE);
+
+  // Pending tree freshness is updated when the new pending tree is committed.
+  state.NotifyReadyToCommit();
+  EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_COMMIT);
+  EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_NONE);
+  EXPECT_FALSE(state.CommitPending());
+  EXPECT_TRUE(state.has_pending_tree());
+  EXPECT_SEQUENCE_NUMBERS(11u, 10u, 10u, BeginFrameArgs::kInvalidFrameNumber,
+                          BeginFrameArgs::kInvalidFrameNumber);
+
+  // If no further BeginMainFrame is needed, OnBeginFrameImplDeadline()
+  // updates the pending tree's frame number.
+  state.OnBeginImplFrame(0, 12);
+  EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_NONE);
+  EXPECT_SEQUENCE_NUMBERS(12u, 10u, 10u, BeginFrameArgs::kInvalidFrameNumber,
+                          BeginFrameArgs::kInvalidFrameNumber);
+  state.OnBeginImplFrameDeadline();
+  EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_NONE);
+  EXPECT_SEQUENCE_NUMBERS(12u, 10u, 12u, BeginFrameArgs::kInvalidFrameNumber,
+                          BeginFrameArgs::kInvalidFrameNumber);
+  state.OnBeginImplFrameIdle();
+  EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_NONE);
+
+  // If a further BeginMainFrame is needed, OnBeginFrameImplDeadline()
+  // updates no freshness numbers.
+  state.SetNeedsBeginMainFrameForTest(true);
+  EXPECT_TRUE(state.NeedsCommit());
+  state.OnBeginImplFrame(0, 13);
+  // BMF will be sent only after pending_tree activation.
+  EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_NONE);
+  state.OnBeginImplFrameDeadline();
+  EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_NONE);
+  EXPECT_SEQUENCE_NUMBERS(13u, 10u, 12u, BeginFrameArgs::kInvalidFrameNumber,
+                          BeginFrameArgs::kInvalidFrameNumber);
+  state.OnBeginImplFrameIdle();
+  EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_NONE);
+
+  // Active tree freshness is updated when pending frame is activated.
+  state.NotifyReadyToActivate();
+  EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_ACTIVATE_SYNC_TREE);
+  EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_NONE);
+  EXPECT_FALSE(state.has_pending_tree());
+  EXPECT_SEQUENCE_NUMBERS(13u, 10u, 12u, 12u,
+                          BeginFrameArgs::kInvalidFrameNumber);
+  EXPECT_TRUE(state.RedrawPending());
+
+  // BMF requested above will be sent after activation.
+  state.OnBeginImplFrame(0, 14);
+  EXPECT_ACTION_UPDATE_STATE(
+      SchedulerStateMachine::ACTION_SEND_BEGIN_MAIN_FRAME);
+  EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_NONE);
+
+  // Active tree freshness is updated when commit didn't have updates, but
+  // compositor frame freshness is not updated.
+  state.NotifyBeginMainFrameStarted();
+  state.BeginMainFrameAborted(CommitEarlyOutReason::FINISHED_NO_UPDATES);
+  EXPECT_SEQUENCE_NUMBERS(14u, 14u, 12u, 14u,
+                          BeginFrameArgs::kInvalidFrameNumber);
+
+  // Compositor frame freshness is updated when active tree is drawn.
+  state.OnBeginImplFrameDeadline();
+  EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_DRAW_IF_POSSIBLE);
+  EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_NONE);
+  EXPECT_FALSE(state.RedrawPending());
+  state.DidSubmitCompositorFrame();
+  state.DidReceiveCompositorFrameAck();
+  EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_NONE);
+  EXPECT_SEQUENCE_NUMBERS(14u, 14u, 12u, 14u, 14u);
+  state.OnBeginImplFrameIdle();
+  EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_NONE);
+
+  // When no updates are required, OnBeginImplFrameDeadline() updates active
+  // tree and compositor frame freshness.
+  state.OnBeginImplFrame(0, 15);
+  EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_NONE);
+  state.OnBeginImplFrameDeadline();
+  EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_NONE);
+  EXPECT_SEQUENCE_NUMBERS(15u, 14u, 12u, 15u, 15u);
+  state.OnBeginImplFrameIdle();
+  EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_NONE);
+
+  // Active tree and compositor frame freshness are updated when commit doesn't
+  // have updates and compositor frame was fresh before.
+  state.SetNeedsBeginMainFrameForTest(true);
+  EXPECT_TRUE(state.NeedsCommit());
+  state.OnBeginImplFrame(0, 16);
+  EXPECT_ACTION_UPDATE_STATE(
+      SchedulerStateMachine::ACTION_SEND_BEGIN_MAIN_FRAME);
+  EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_NONE);
+  EXPECT_FALSE(state.NeedsCommit());
+  EXPECT_TRUE(state.CommitPending());
+  state.NotifyBeginMainFrameStarted();
+  state.BeginMainFrameAborted(CommitEarlyOutReason::FINISHED_NO_UPDATES);
+  EXPECT_SEQUENCE_NUMBERS(16u, 16u, 12u, 16u, 16u);
+  state.OnBeginImplFrameDeadline();
+  EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_NONE);
+  EXPECT_SEQUENCE_NUMBERS(16u, 16u, 12u, 16u, 16u);
+  state.OnBeginImplFrameIdle();
+  EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_NONE);
+
+  // When the source changes, the current frame number is updated and frame
+  // numbers for freshness are reset to invalid numbers.
+  state.OnBeginImplFrame(1, 5);
+  EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_NONE);
+  EXPECT_SEQUENCE_NUMBERS(5u, BeginFrameArgs::kInvalidFrameNumber,
+                          BeginFrameArgs::kInvalidFrameNumber,
+                          BeginFrameArgs::kInvalidFrameNumber,
+                          BeginFrameArgs::kInvalidFrameNumber);
+
+  // When no updates are required, OnBeginImplFrameDeadline() updates active
+  // tree and compositor frame freshness.
+  state.OnBeginImplFrameDeadline();
+  EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_NONE);
+  EXPECT_SEQUENCE_NUMBERS(5u, BeginFrameArgs::kInvalidFrameNumber,
+                          BeginFrameArgs::kInvalidFrameNumber, 5u, 5u);
+  state.OnBeginImplFrameIdle();
+  EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_NONE);
+}
+
+TEST(SchedulerStateMachineTest,
+     TestBeginFrameFreshnessWithNoUpdatesCommitAndPendingTree) {
+  // Setup with main_frame_before_activation_enabled, a pending tree, and a
+  // new BeginMainFrame requested.
+  SchedulerSettings settings;
+  settings.main_frame_before_activation_enabled = true;
+  StateMachine state(settings);
+  SET_UP_STATE(state)
+  state.SetHasPendingTree(true);
+  state.SetNeedsRedraw(false);
+  state.SetNeedsBeginMainFrameForTest(true);
+  EXPECT_FALSE(state.RedrawPending());
+  EXPECT_TRUE(state.NeedsCommit());
+
+  // OnBeginImplFrame() updates the sequence number, WillSendBeginMainFrame()
+  // updates begin_main_frame_sent sequence number.
+  state.OnBeginImplFrame(0, 10);
+  EXPECT_ACTION_UPDATE_STATE(
+      SchedulerStateMachine::ACTION_SEND_BEGIN_MAIN_FRAME);
+  EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_NONE);
+  EXPECT_FALSE(state.NeedsCommit());
+  EXPECT_TRUE(state.CommitPending());
+  EXPECT_SEQUENCE_NUMBERS(10u, 10u, BeginFrameArgs::kInvalidFrameNumber,
+                          BeginFrameArgs::kInvalidFrameNumber,
+                          BeginFrameArgs::kInvalidFrameNumber);
+
+  // Pending tree freshness is updated when commit didn't have updates, but an
+  // older pending tree is still pending.
+  state.NotifyBeginMainFrameStarted();
+  state.BeginMainFrameAborted(CommitEarlyOutReason::FINISHED_NO_UPDATES);
+  EXPECT_SEQUENCE_NUMBERS(10u, 10u, 10u, BeginFrameArgs::kInvalidFrameNumber,
+                          BeginFrameArgs::kInvalidFrameNumber);
+
+  // As no further BeginMainFrame is needed, OnBeginFrameImplDeadline()
+  // updates the pending tree's frame number, but without any visible change.
+  state.OnBeginImplFrameDeadline();
+  EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_NONE);
+  EXPECT_SEQUENCE_NUMBERS(10u, 10u, 10u, BeginFrameArgs::kInvalidFrameNumber,
+                          BeginFrameArgs::kInvalidFrameNumber);
+  state.OnBeginImplFrameIdle();
+  EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_NONE);
+}
+
 }  // namespace
 }  // namespace cc