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

cc/scheduler/scheduler_state_machine_unittest.cc

Index: cc/scheduler/scheduler_state_machine_unittest.cc
diff --git a/cc/scheduler/scheduler_state_machine_unittest.cc b/cc/scheduler/scheduler_state_machine_unittest.cc
index aa5c4aac39a1164318196bfee92197fcbc1a2909..8d414a2770bedb888e42fa2b5c3101aefbe6d422 100644
--- a/cc/scheduler/scheduler_state_machine_unittest.cc
+++ b/cc/scheduler/scheduler_state_machine_unittest.cc
@@ -7,6 +7,7 @@
 #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"
@@ -22,6 +23,19 @@
   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())        \
@@ -86,6 +100,10 @@ class StateMachine : public SchedulerStateMachine {
     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;
   }
@@ -150,12 +168,26 @@ class StateMachine : public SchedulerStateMachine {
     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) {
@@ -271,7 +303,7 @@ TEST(SchedulerStateMachineTest, TestNextActionBeginsMainFrameIfNeeded) {
     EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_NONE);
     EXPECT_FALSE(state.NeedsCommit());
 
-    state.OnBeginImplFrame();
+    state.IssueNextBeginImplFrame();
     EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_NONE);
 
     state.OnBeginImplFrameDeadline();
@@ -290,7 +322,7 @@ TEST(SchedulerStateMachineTest, TestNextActionBeginsMainFrameIfNeeded) {
     EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_NONE);
     EXPECT_TRUE(state.NeedsCommit());
 
-    state.OnBeginImplFrame();
+    state.IssueNextBeginImplFrame();
     EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_NONE);
 
     state.OnBeginImplFrameDeadline();
@@ -318,7 +350,7 @@ TEST(SchedulerStateMachineTest, TestNextActionBeginsMainFrameIfNeeded) {
     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);
@@ -345,7 +377,7 @@ TEST(SchedulerStateMachineTest, TestNextActionBeginsMainFrameIfNeeded) {
     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);
@@ -367,7 +399,7 @@ TEST(SchedulerStateMachineTest, MainFrameBeforeActivationEnabled) {
   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);
@@ -383,7 +415,7 @@ TEST(SchedulerStateMachineTest, MainFrameBeforeActivationEnabled) {
 
   // 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);
@@ -420,7 +452,7 @@ TEST(SchedulerStateMachineTest,
   EXPECT_TRUE(state.BeginFrameNeeded());
 
   // Start a frame.
-  state.OnBeginImplFrame();
+  state.IssueNextBeginImplFrame();
   EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_NONE);
   EXPECT_FALSE(state.CommitPending());
 
@@ -438,7 +470,7 @@ TEST(SchedulerStateMachineTest,
   // 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);
@@ -457,7 +489,7 @@ TEST(SchedulerStateMachineTest, FailedDrawForMissingHighResNeedsCommit) {
   EXPECT_TRUE(state.BeginFrameNeeded());
 
   // Start a frame.
-  state.OnBeginImplFrame();
+  state.IssueNextBeginImplFrame();
   EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_NONE);
   EXPECT_FALSE(state.CommitPending());
 
@@ -475,7 +507,7 @@ TEST(SchedulerStateMachineTest, FailedDrawForMissingHighResNeedsCommit) {
   // 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);
@@ -493,7 +525,7 @@ TEST(SchedulerStateMachineTest, FailedDrawForMissingHighResNeedsCommit) {
   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);
@@ -514,7 +546,7 @@ TEST(SchedulerStateMachineTest,
   // 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);
@@ -545,7 +577,7 @@ TEST(SchedulerStateMachineTest,
   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);
@@ -569,7 +601,7 @@ TEST(SchedulerStateMachineTest, TestFailedDrawsDoNotRestartForcedDraw) {
   // 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);
@@ -583,7 +615,7 @@ TEST(SchedulerStateMachineTest, TestFailedDrawsDoNotRestartForcedDraw) {
   // 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);
@@ -604,7 +636,7 @@ TEST(SchedulerStateMachineTest, TestFailedDrawsDoNotRestartForcedDraw) {
   // 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);
@@ -626,7 +658,7 @@ TEST(SchedulerStateMachineTest, TestFailedDrawIsRetriedInNextBeginImplFrame) {
   // 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());
@@ -641,7 +673,7 @@ TEST(SchedulerStateMachineTest, TestFailedDrawIsRetriedInNextBeginImplFrame) {
 
   // 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
@@ -662,7 +694,7 @@ TEST(SchedulerStateMachineTest, TestDoestDrawTwiceInSameFrame) {
 
   // Draw the first frame.
   EXPECT_TRUE(state.BeginFrameNeeded());
-  state.OnBeginImplFrame();
+  state.IssueNextBeginImplFrame();
   EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_NONE);
 
   state.OnBeginImplFrameDeadline();
@@ -678,7 +710,7 @@ TEST(SchedulerStateMachineTest, TestDoestDrawTwiceInSameFrame) {
 
   // 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);
@@ -816,7 +848,7 @@ TEST(SchedulerStateMachineTest, TestCanRedraw_StopsDraw) {
       state.SetVisible(false);
       state.SetNeedsRedraw(true);
       if (j == 1)
-        state.OnBeginImplFrame();
+        state.IssueNextBeginImplFrame();
 
       state.SetCanDraw(false);
       EXPECT_NE(SchedulerStateMachine::ACTION_DRAW_IF_POSSIBLE,
@@ -839,7 +871,7 @@ TEST(SchedulerStateMachineTest,
   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);
@@ -863,7 +895,7 @@ TEST(SchedulerStateMachineTest, TestSetNeedsBeginMainFrameIsNotLost) {
   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);
@@ -892,7 +924,7 @@ TEST(SchedulerStateMachineTest, TestSetNeedsBeginMainFrameIsNotLost) {
   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);
@@ -924,7 +956,7 @@ TEST(SchedulerStateMachineTest, TestFullCycle) {
   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);
@@ -970,7 +1002,7 @@ TEST(SchedulerStateMachineTest, CommitWithoutDrawWithPendingTree) {
   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();
@@ -983,7 +1015,7 @@ TEST(SchedulerStateMachineTest, CommitWithoutDrawWithPendingTree) {
   // 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();
@@ -1002,7 +1034,7 @@ TEST(SchedulerStateMachineTest, DontCommitWithoutDrawWithoutPendingTree) {
   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();
@@ -1014,7 +1046,7 @@ TEST(SchedulerStateMachineTest, DontCommitWithoutDrawWithoutPendingTree) {
   // 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.IssueNextBeginImplFrame();
   EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_NONE);
 }
 
@@ -1026,7 +1058,7 @@ TEST(SchedulerStateMachineTest, AbortedMainFrameDoesNotResetPendingTree) {
 
   // 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);
@@ -1041,7 +1073,7 @@ TEST(SchedulerStateMachineTest, AbortedMainFrameDoesNotResetPendingTree) {
   // 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);
@@ -1055,7 +1087,7 @@ TEST(SchedulerStateMachineTest, AbortedMainFrameDoesNotResetPendingTree) {
 
   // 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);
@@ -1084,7 +1116,7 @@ TEST(SchedulerStateMachineTest, TestFullCycleWithCommitToActive) {
   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);
@@ -1111,7 +1143,7 @@ TEST(SchedulerStateMachineTest, TestFullCycleWithCommitToActive) {
 
   // Can't BeginMainFrame yet since last commit hasn't been drawn yet.
   state.SetNeedsBeginMainFrame();
-  state.OnBeginImplFrame();
+  state.IssueNextBeginImplFrame();
   EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_NONE);
 
   // Now call ready to draw which will allow the draw to happen and
@@ -1124,7 +1156,7 @@ TEST(SchedulerStateMachineTest, TestFullCycleWithCommitToActive) {
   EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_NONE);
 
   // Can't BeginMainFrame yet since we're submit-frame throttled.
-  state.OnBeginImplFrame();
+  state.IssueNextBeginImplFrame();
   EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_NONE);
 
   // CompositorFrameAck unblocks BeginMainFrame.
@@ -1154,7 +1186,7 @@ TEST(SchedulerStateMachineTest, TestFullCycleWithCommitRequestInbetween) {
   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);
@@ -1193,7 +1225,7 @@ TEST(SchedulerStateMachineTest, TestFullCycleWithCommitRequestInbetween) {
   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);
 }
@@ -1256,7 +1288,7 @@ TEST(SchedulerStateMachineTest, TestAbortBeginMainFrameBecauseInvisible) {
   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);
@@ -1290,7 +1322,7 @@ TEST(SchedulerStateMachineTest, TestAbortBeginMainFrameBecauseInvisible) {
   EXPECT_TRUE(state.NeedsCommit());
 
   // Start a new frame.
-  state.OnBeginImplFrame();
+  state.IssueNextBeginImplFrame();
   EXPECT_ACTION_UPDATE_STATE(
       SchedulerStateMachine::ACTION_SEND_BEGIN_MAIN_FRAME);
 
@@ -1312,7 +1344,7 @@ TEST(SchedulerStateMachineTest, TestAbortBeginMainFrameBecauseCommitNotNeeded) {
 
   // 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);
@@ -1336,7 +1368,7 @@ TEST(SchedulerStateMachineTest, TestAbortBeginMainFrameBecauseCommitNotNeeded) {
   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);
@@ -1344,7 +1376,7 @@ TEST(SchedulerStateMachineTest, TestAbortBeginMainFrameBecauseCommitNotNeeded) {
   // 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);
 }
 
@@ -1360,14 +1392,14 @@ TEST(SchedulerStateMachineTest, TestFirstContextCreation) {
   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);
 }
@@ -1392,7 +1424,7 @@ TEST(SchedulerStateMachineTest, TestContextLostWhenCompletelyIdle) {
   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);
 }
@@ -1414,14 +1446,14 @@ TEST(SchedulerStateMachineTest,
   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);
@@ -1438,7 +1470,7 @@ TEST(SchedulerStateMachineTest,
   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);
@@ -1464,7 +1496,7 @@ TEST(SchedulerStateMachineTest,
   // 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);
@@ -1472,7 +1504,7 @@ TEST(SchedulerStateMachineTest,
   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);
@@ -1480,7 +1512,7 @@ TEST(SchedulerStateMachineTest,
   // 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);
@@ -1494,7 +1526,7 @@ TEST(SchedulerStateMachineTest,
   // 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);
@@ -1526,7 +1558,7 @@ TEST(SchedulerStateMachineTest, TestContextLostWhileCommitInProgress) {
 
   // 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);
@@ -1560,7 +1592,7 @@ TEST(SchedulerStateMachineTest, TestContextLostWhileCommitInProgress) {
   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);
@@ -1583,7 +1615,7 @@ TEST(SchedulerStateMachineTest,
 
   // 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);
@@ -1617,7 +1649,7 @@ TEST(SchedulerStateMachineTest,
   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);
@@ -1633,7 +1665,7 @@ TEST(SchedulerStateMachineTest,
 
   // 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);
@@ -1667,7 +1699,7 @@ TEST(SchedulerStateMachineTest,
   state.DidCreateAndInitializeCompositorFrameSink();
 
   EXPECT_FALSE(state.RedrawPending());
-  state.OnBeginImplFrame();
+  state.IssueNextBeginImplFrame();
   EXPECT_ACTION(SchedulerStateMachine::ACTION_SEND_BEGIN_MAIN_FRAME);
 }
 
@@ -1730,7 +1762,7 @@ TEST(SchedulerStateMachineTest, TestNoBeginMainFrameWhenInvisible) {
   // 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);
 }
@@ -1894,7 +1926,7 @@ TEST(SchedulerStateMachineTest,
 
   // 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.
@@ -1929,7 +1961,7 @@ void FinishPreviousCommitAndDrawWithoutExitingDeadline(
   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());
@@ -1947,7 +1979,7 @@ TEST(SchedulerStateMachineTest, TestImplLatencyTakesPriority) {
   // 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);
@@ -1984,7 +2016,7 @@ TEST(SchedulerStateMachineTest, TestImplLatencyTakesPriority) {
   // 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();
@@ -1999,7 +2031,7 @@ TEST(SchedulerStateMachineTest,
 
   state.SetNeedsBeginMainFrame();
 
-  state.OnBeginImplFrame();
+  state.IssueNextBeginImplFrame();
   EXPECT_ACTION_UPDATE_STATE(
       SchedulerStateMachine::ACTION_SEND_BEGIN_MAIN_FRAME);
   EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_NONE);
@@ -2019,7 +2051,7 @@ TEST(SchedulerStateMachineTest, TestTriggerDeadlineImmediatelyWhenInvisible) {
 
   state.SetNeedsBeginMainFrame();
 
-  state.OnBeginImplFrame();
+  state.IssueNextBeginImplFrame();
   EXPECT_ACTION_UPDATE_STATE(
       SchedulerStateMachine::ACTION_SEND_BEGIN_MAIN_FRAME);
   EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_NONE);
@@ -2039,7 +2071,7 @@ TEST(SchedulerStateMachineTest,
 
   state.SetNeedsBeginMainFrame();
 
-  state.OnBeginImplFrame();
+  state.IssueNextBeginImplFrame();
   EXPECT_ACTION_UPDATE_STATE(
       SchedulerStateMachine::ACTION_SEND_BEGIN_MAIN_FRAME);
   EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_NONE);
@@ -2062,14 +2094,14 @@ TEST(SchedulerStateMachineTest, TestDeferCommit) {
   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);
 }
@@ -2083,7 +2115,7 @@ TEST(SchedulerStateMachineTest, EarlyOutCommitWantsProactiveBeginFrame) {
   bool commit_has_no_updates = true;
   state.WillCommit(commit_has_no_updates);
   EXPECT_TRUE(state.ProactiveBeginFrameWanted());
-  state.OnBeginImplFrame();
+  state.IssueNextBeginImplFrame();
   EXPECT_FALSE(state.ProactiveBeginFrameWanted());
 }
 
@@ -2095,7 +2127,7 @@ TEST(SchedulerStateMachineTest,
 
   // 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.
@@ -2123,5 +2155,266 @@ TEST(SchedulerStateMachineTest,
       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 a valid current frame number, but invalid frame
+  // numbers for freshness.
+  EXPECT_SEQUENCE_NUMBERS(
+      BeginFrameArgs::kStartingFrameNumber, 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);
+  state.OnBeginImplFrameDeadline();
+  EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_NONE);
+  EXPECT_SEQUENCE_NUMBERS(12u, 10u, 12u, BeginFrameArgs::kInvalidFrameNumber,

[brianderson, 2017/02/15 00:13:54]

Can you verify that before the deadline, the pending tree's frame number hasn't
been updated? (Just in case SetNeedsCommit arrives before the deadline.)

[Eric Seckler, 2017/02/17 00:07:27]

Done.

+                          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.
+  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);
+
+  // 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