cc: Heuristic for Renderer latency recovery

cc/scheduler/scheduler_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.h"
 
 #include <string>
 #include <vector>
 
 #include "base/logging.h"
@@ skipping 228 matching lines @@
     scoped_ptr<FakeCompositorTimingHistory> fake_compositor_timing_history =
         FakeCompositorTimingHistory::Create();
     fake_compositor_timing_history_ = fake_compositor_timing_history.get();
 
     scheduler_ = TestScheduler::Create(
         now_src_.get(), client_.get(), scheduler_settings_, 0,
         task_runner_.get(), fake_external_begin_frame_source_.get(),
         fake_compositor_timing_history.Pass());
     DCHECK(scheduler_);
     client_->set_scheduler(scheduler_.get());
+
+    // Use large estimates by default to avoid latency recovery
+    // in most tests.
+    base::TimeDelta one_second = base::TimeDelta::FromSeconds(1);
+    fake_compositor_timing_history_->SetBeginMainFrameToCommitDurationEstimate(
+        one_second);
+    fake_compositor_timing_history_->SetCommitToReadyToActivateDurationEstimate(
+        one_second);
+    fake_compositor_timing_history_->SetDrawDurationEstimate(one_second);
+
     return scheduler_.get();
   }
 
   void CreateSchedulerAndInitSurface() {
     CreateScheduler();
     EXPECT_SCOPED(InitializeOutputSurfaceAndFirstCommit());
   }
 
   void SetUpScheduler(bool initSurface) {
     SetUpScheduler(make_scoped_ptr(new FakeSchedulerClient), initSurface);
@@ skipping 118 matching lines @@
     BeginFrameArgs args =
         CreateBeginFrameArgsForTesting(BEGINFRAME_FROM_HERE, now_src());
     fake_external_begin_frame_source_->TestOnBeginFrame(args);
     return args;
   }
 
   FakeExternalBeginFrameSource* fake_external_begin_frame_source() const {
     return fake_external_begin_frame_source_.get();
   }
 
-  void MainFrameInHighLatencyMode(
-      int64 begin_main_frame_to_commit_estimate_in_ms,
-      int64 commit_to_activate_estimate_in_ms,
-      bool impl_latency_takes_priority,
-      bool should_send_begin_main_frame);
+  void MainFrameInHighLatencyMode(bool should_send_begin_main_frame);
+  void ImplFrameInHighLatencySkipImplFrame(bool swap_ack_before_deadline);
+  void ImplFrameInHighLatencyDontSkipImplFrame();
   void BeginFramesNotFromClient(bool use_external_begin_frame_source,
                                 bool throttle_frame_production);
   void BeginFramesNotFromClient_SwapThrottled(
       bool use_external_begin_frame_source,
       bool throttle_frame_production);
 
   scoped_ptr<base::SimpleTestTickClock> now_src_;
   scoped_refptr<OrderedSimpleTaskRunner> task_runner_;
   scoped_ptr<FakeExternalBeginFrameSource> fake_external_begin_frame_source_;
   SchedulerSettings scheduler_settings_;
@@ skipping 880 matching lines @@
   // Scheduler loses output surface, and stops waiting for ready to draw signal.
   client_->Reset();
   scheduler_->DidLoseOutputSurface();
   EXPECT_TRUE(scheduler_->BeginImplFrameDeadlinePending());
   task_runner().RunPendingTasks();  // Run posted deadline.
   EXPECT_ACTION("ScheduledActionBeginOutputSurfaceCreation", client_, 0, 3);
   EXPECT_ACTION("SetNeedsBeginFrames(false)", client_, 1, 3);
   EXPECT_ACTION("SendBeginMainFrameNotExpectedSoon", client_, 2, 3);
 }
 
 void SchedulerTest::MainFrameInHighLatencyMode(

[mithro-old, 2015/07/08 00:54:51]

nit: I think this could be named better.

My thought is that this method checks what happens to a BeginMainFrame *after*
making commit missing an impl frame deadline. Hence something like Check (XXXXX)
After (doing YYYY) - IE

 CheckBeginMainFrameAfterMakingCommitMissImplDeadline(bool
expect_send_begin_main_frame);

Then a person doesn't even have to understand what is meant by
"InHighLatencyMode".

-    int64 begin_main_frame_to_commit_estimate_in_ms,
-    int64 commit_to_activate_estimate_in_ms,
-    bool impl_latency_takes_priority,
-    bool should_send_begin_main_frame) {
-  scheduler_settings_.use_external_begin_frame_source = true;
-  SetUpScheduler(true);
-
-  fake_compositor_timing_history_->SetBeginMainFrameToCommitDurationEstimate(
-      base::TimeDelta::FromMilliseconds(
-          begin_main_frame_to_commit_estimate_in_ms));
-  fake_compositor_timing_history_->SetCommitToReadyToActivateDurationEstimate(
-      base::TimeDelta::FromMilliseconds(commit_to_activate_estimate_in_ms));
-  fake_compositor_timing_history_->SetDrawDurationEstimate(
-      base::TimeDelta::FromMilliseconds(1));
-
-  scheduler_->SetImplLatencyTakesPriority(impl_latency_takes_priority);
-
+    bool expect_send_begin_main_frame) {
   // Impl thread hits deadline before commit finishes.
   scheduler_->SetNeedsCommit();
   EXPECT_FALSE(scheduler_->MainThreadIsInHighLatencyMode());
   EXPECT_SCOPED(AdvanceFrame());
   EXPECT_FALSE(scheduler_->MainThreadIsInHighLatencyMode());
   task_runner().RunPendingTasks();  // Run posted deadline.
   EXPECT_TRUE(scheduler_->MainThreadIsInHighLatencyMode());
   scheduler_->NotifyBeginMainFrameStarted();
   scheduler_->NotifyReadyToCommit();
   scheduler_->NotifyReadyToActivate();
   EXPECT_TRUE(scheduler_->MainThreadIsInHighLatencyMode());
   EXPECT_TRUE(client_->HasAction("ScheduledActionSendBeginMainFrame"));
 
   client_->Reset();
   scheduler_->SetNeedsCommit();
   EXPECT_TRUE(scheduler_->MainThreadIsInHighLatencyMode());
   EXPECT_SCOPED(AdvanceFrame());
   EXPECT_TRUE(scheduler_->MainThreadIsInHighLatencyMode());
   task_runner().RunPendingTasks();  // Run posted deadline.
-  EXPECT_EQ(scheduler_->MainThreadIsInHighLatencyMode(),
-            should_send_begin_main_frame);
-  EXPECT_EQ(client_->HasAction("ScheduledActionSendBeginMainFrame"),
-            should_send_begin_main_frame);
+  EXPECT_EQ(expect_send_begin_main_frame,
+            scheduler_->MainThreadIsInHighLatencyMode());
+  EXPECT_EQ(expect_send_begin_main_frame,
+            client_->HasAction("ScheduledActionSendBeginMainFrame"));
+}
+
+TEST_F(SchedulerTest, SkipMainFrameIfHighLatencyAndCanDrawBeforeDeadline) {

[mithro-old, 2015/07/08 00:54:51]

nit: s/IfHighLatency/IfLateCommit/ or maybe IfMissCommit?

+  scheduler_settings_.use_external_begin_frame_source = true;
+  SetUpScheduler(true);
+
+  auto fast_duration = base::TimeDelta::FromMilliseconds(1);
+  fake_compositor_timing_history_->SetAllEstimatesTo(fast_duration);
+
+  bool expect_send_begin_main_frame = false;
+  EXPECT_SCOPED(MainFrameInHighLatencyMode(expect_send_begin_main_frame));
+}
+
+TEST_F(SchedulerTest, DontSkipMainFrameInPreferImplLatencyMode) {
+  scheduler_settings_.use_external_begin_frame_source = true;
+  SetUpScheduler(true);
+  scheduler_->SetImplLatencyTakesPriority(true);
+
+  auto fast_duration = base::TimeDelta::FromMilliseconds(1);
+  fake_compositor_timing_history_->SetAllEstimatesTo(fast_duration);
+
+  bool expect_send_begin_main_frame = true;
+  EXPECT_SCOPED(MainFrameInHighLatencyMode(expect_send_begin_main_frame));
+}
+
+TEST_F(SchedulerTest, DontSkipMainFrameIfCommitEstimateTooLong) {
+  scheduler_settings_.use_external_begin_frame_source = true;
+  SetUpScheduler(true);
+  fake_compositor_timing_history_->SetAllEstimatesTo(base::TimeDelta());

[mithro-old, 2015/07/08 00:54:51]

nit: It seems like it could be dangerous to be using zero TimeDelta estimates
here?

+  fake_compositor_timing_history_->SetBeginMainFrameToCommitDurationEstimate(
+      base::TimeDelta::FromMilliseconds(16));

[mithro-old, 2015/07/08 00:54:51]

nit: Should we use a larger value here?

+  bool expect_send_begin_main_frame = true;
+  EXPECT_SCOPED(MainFrameInHighLatencyMode(expect_send_begin_main_frame));
+}
+
+TEST_F(SchedulerTest, DontSkipMainFrameIfReadyToActivateEstimateTooLong) {
+  scheduler_settings_.use_external_begin_frame_source = true;
+  SetUpScheduler(true);
+  fake_compositor_timing_history_->SetAllEstimatesTo(base::TimeDelta());
+  fake_compositor_timing_history_->SetCommitToReadyToActivateDurationEstimate(
+      base::TimeDelta::FromMilliseconds(16));
+  bool expect_send_begin_main_frame = true;
+  EXPECT_SCOPED(MainFrameInHighLatencyMode(expect_send_begin_main_frame));
+}
+
+TEST_F(SchedulerTest, DontSkipMainFrameIfActivateEstimateTooLong) {
+  scheduler_settings_.use_external_begin_frame_source = true;
+  SetUpScheduler(true);
+  fake_compositor_timing_history_->SetAllEstimatesTo(base::TimeDelta());
+  fake_compositor_timing_history_->SetActivateDurationEstimate(
+      base::TimeDelta::FromMilliseconds(16));
+  bool expect_send_begin_main_frame = true;
+  EXPECT_SCOPED(MainFrameInHighLatencyMode(expect_send_begin_main_frame));
+}
+
+TEST_F(SchedulerTest, DontSkipMainFrameIfDrawEstimateTooLong) {
+  scheduler_settings_.use_external_begin_frame_source = true;
+  SetUpScheduler(true);
+  fake_compositor_timing_history_->SetAllEstimatesTo(base::TimeDelta());
+  fake_compositor_timing_history_->SetDrawDurationEstimate(
+      base::TimeDelta::FromMilliseconds(16));
+  bool expect_send_begin_main_frame = true;
+  EXPECT_SCOPED(MainFrameInHighLatencyMode(expect_send_begin_main_frame));
+}
+
+void SchedulerTest::ImplFrameInHighLatencySkipImplFrame(

[mithro-old, 2015/07/08 00:54:51]

nit: Name - see comments above too.

+    bool swap_ack_before_deadline) {
+  // Set up client with specified estimates.
+  scheduler_settings_.use_external_begin_frame_source = true;
+  SetUpScheduler(true);
+
+  // Use estimates that indicate commit and activate can finish before the
+  // deadline.
+  auto fast_duration = base::TimeDelta::FromMilliseconds(1);
+  fake_compositor_timing_history_->SetAllEstimatesTo(fast_duration);
+
+  // To get into a high latency state, this test disables automatic swap acks.
+  scheduler_->SetMaxSwapsPending(1);
+  client_->SetAutomaticSwapAck(false);
+
+  // Draw and swap for first BeginFrame
+  client_->Reset();
+  scheduler_->SetNeedsCommit();
+  scheduler_->SetNeedsRedraw();
+  EXPECT_FALSE(scheduler_->MainThreadIsInHighLatencyMode());
+  SendNextBeginFrame();
+  EXPECT_ACTION("SetNeedsBeginFrames(true)", client_, 0, 4);
+  EXPECT_ACTION("WillBeginImplFrame", client_, 1, 4);
+  EXPECT_ACTION("ScheduledActionAnimate", client_, 2, 4);
+  EXPECT_ACTION("ScheduledActionSendBeginMainFrame", client_, 3, 4);
+
+  client_->Reset();
+  scheduler_->NotifyBeginMainFrameStarted();
+  scheduler_->NotifyReadyToCommit();
+  scheduler_->NotifyReadyToActivate();
+  EXPECT_FALSE(scheduler_->MainThreadIsInHighLatencyMode());
+  task_runner().RunTasksWhile(client_->ImplFrameDeadlinePending(true));
+  EXPECT_ACTION("ScheduledActionCommit", client_, 0, 4);
+  EXPECT_ACTION("ScheduledActionActivateSyncTree", client_, 1, 4);
+  EXPECT_ACTION("ScheduledActionAnimate", client_, 2, 4);
+  EXPECT_ACTION("ScheduledActionDrawAndSwapIfPossible", client_, 3, 4);
+
+  // Verify we skip every other frame if the swap ack consistently
+  // comes back late.
+  for (int i = 0; i < 10; i++) {
+    // Not calling scheduler_->DidSwapBuffersComplete() until after next
+    // BeginImplFrame puts the impl thread in high latency mode.
+    client_->Reset();
+    scheduler_->SetNeedsCommit();
+    scheduler_->SetNeedsRedraw();
+    EXPECT_FALSE(scheduler_->MainThreadIsInHighLatencyMode());
+    SendNextBeginFrame();
+    // Verify that we skip the BeginImplFrame
+    EXPECT_NO_ACTION(client_);
+    EXPECT_FALSE(scheduler_->BeginImplFrameDeadlinePending());
+    EXPECT_FALSE(scheduler_->MainThreadIsInHighLatencyMode());
+
+    // Verify that we do not perform any actions after we are no longer
+    // swap throttled.
+    // Also verify the scheduler logic that determines if we are in a high

[mithro-old, 2015/07/08 00:54:51]

Where is the verification that this comment is referring too?

+    // latency mode is immune to whether or not the swap ack comes back before
+    // or after the deadline.
+    client_->Reset();
+    if (swap_ack_before_deadline) {
+      scheduler_->DidSwapBuffersComplete();
+      task_runner().RunTasksWhile(client_->ImplFrameDeadlinePending(true));
+    } else {
+      task_runner().RunTasksWhile(client_->ImplFrameDeadlinePending(true));
+      scheduler_->DidSwapBuffersComplete();
+    }
+    EXPECT_NO_ACTION(client_);
+
+    // Verify that we start the next BeginImplFrame and continue normally
+    // after having just skipped a BeginImplFrame.
+    client_->Reset();
+    EXPECT_FALSE(scheduler_->MainThreadIsInHighLatencyMode());
+    scheduler_->SetNeedsCommit();
+    scheduler_->SetNeedsRedraw();
+    SendNextBeginFrame();
+    EXPECT_ACTION("WillBeginImplFrame", client_, 0, 3);
+    EXPECT_ACTION("ScheduledActionAnimate", client_, 1, 3);
+    EXPECT_ACTION("ScheduledActionSendBeginMainFrame", client_, 2, 3);
+
+    client_->Reset();
+    scheduler_->NotifyBeginMainFrameStarted();
+    scheduler_->NotifyReadyToCommit();
+    scheduler_->NotifyReadyToActivate();
+    task_runner().RunTasksWhile(client_->ImplFrameDeadlinePending(true));
+    EXPECT_ACTION("ScheduledActionCommit", client_, 0, 4);
+    EXPECT_ACTION("ScheduledActionActivateSyncTree", client_, 1, 4);
+    EXPECT_ACTION("ScheduledActionAnimate", client_, 2, 4);
+    EXPECT_ACTION("ScheduledActionDrawAndSwapIfPossible", client_, 3, 4);
+  }
 }
 
 TEST_F(SchedulerTest,
-       SkipMainFrameIfHighLatencyAndCanCommitAndActivateBeforeDeadline) {
-  // Set up client so that estimates indicate that we can commit and activate
-  // before the deadline (~8ms by default).
-  EXPECT_SCOPED(MainFrameInHighLatencyMode(1, 1, false, false));
-}
-
-TEST_F(SchedulerTest, NotSkipMainFrameIfHighLatencyAndCanCommitTooLong) {
-  // Set up client so that estimates indicate that the commit cannot finish
-  // before the deadline (~8ms by default).
-  EXPECT_SCOPED(MainFrameInHighLatencyMode(10, 1, false, true));
-}
-
-TEST_F(SchedulerTest, NotSkipMainFrameIfHighLatencyAndCanActivateTooLong) {
-  // Set up client so that estimates indicate that the activate cannot finish
-  // before the deadline (~8ms by default).
-  EXPECT_SCOPED(MainFrameInHighLatencyMode(1, 10, false, true));
-}
-
-TEST_F(SchedulerTest, NotSkipMainFrameInPreferImplLatencyMode) {
-  // Set up client so that estimates indicate that we can commit and activate
-  // before the deadline (~8ms by default), but also enable impl latency takes
-  // priority mode.
-  EXPECT_SCOPED(MainFrameInHighLatencyMode(1, 1, true, true));
+       SkipSwapIfHighLatencyAndCanDrawBeforeDeadline_SwapAckThenDeadline) {
+  bool swap_ack_before_deadline = true;
+  EXPECT_SCOPED(ImplFrameInHighLatencySkipImplFrame(swap_ack_before_deadline));
+}
+
+TEST_F(SchedulerTest,
+       SkipSwapIfHighLatencyAndCanDrawBeforeDeadline_DeadlineThenSwapAck) {
+  bool swap_ack_before_deadline = false;
+  EXPECT_SCOPED(ImplFrameInHighLatencySkipImplFrame(swap_ack_before_deadline));
+}
+
+void SchedulerTest::ImplFrameInHighLatencyDontSkipImplFrame() {
+  // To get into a high latency state, this test disables automatic swap acks.
+  scheduler_->SetMaxSwapsPending(1);
+  client_->SetAutomaticSwapAck(false);
+
+  // Draw and swap for first BeginFrame
+  client_->Reset();
+  scheduler_->SetNeedsCommit();
+  EXPECT_FALSE(scheduler_->MainThreadIsInHighLatencyMode());
+  SendNextBeginFrame();
+  EXPECT_ACTION("SetNeedsBeginFrames(true)", client_, 0, 3);
+  EXPECT_ACTION("WillBeginImplFrame", client_, 1, 3);
+  EXPECT_ACTION("ScheduledActionSendBeginMainFrame", client_, 2, 3);
+
+  client_->Reset();
+  scheduler_->NotifyBeginMainFrameStarted();
+  scheduler_->NotifyReadyToCommit();
+  scheduler_->NotifyReadyToActivate();
+  EXPECT_FALSE(scheduler_->MainThreadIsInHighLatencyMode());
+  task_runner().RunTasksWhile(client_->ImplFrameDeadlinePending(true));
+  EXPECT_ACTION("ScheduledActionCommit", client_, 0, 4);
+  EXPECT_ACTION("ScheduledActionActivateSyncTree", client_, 1, 4);
+  EXPECT_ACTION("ScheduledActionAnimate", client_, 2, 4);
+  EXPECT_ACTION("ScheduledActionDrawAndSwapIfPossible", client_, 3, 4);
+
+  // Verify impl thread consistently operates in high latency mode
+  // without skipping any frames.
+  for (int i = 0; i < 10; i++) {
+    // Not calling scheduler_->DidSwapBuffersComplete() until after next frame
+    // puts the impl thread in high latency mode.
+    client_->Reset();
+    scheduler_->SetNeedsCommit();
+    EXPECT_FALSE(scheduler_->MainThreadIsInHighLatencyMode());
+    SendNextBeginFrame();
+    EXPECT_SINGLE_ACTION("WillBeginImplFrame", client_);
+    EXPECT_TRUE(scheduler_->BeginImplFrameDeadlinePending());
+    EXPECT_FALSE(scheduler_->MainThreadIsInHighLatencyMode());
+
+    client_->Reset();
+    scheduler_->DidSwapBuffersComplete();
+    scheduler_->NotifyBeginMainFrameStarted();
+    scheduler_->NotifyReadyToCommit();
+    scheduler_->NotifyReadyToActivate();
+    task_runner().RunTasksWhile(client_->ImplFrameDeadlinePending(true));
+
+    // Verify that we don't skip the actions of the BeginImplFrame
+    EXPECT_ACTION("ScheduledActionSendBeginMainFrame", client_, 0, 5);
+    EXPECT_ACTION("ScheduledActionCommit", client_, 1, 5);
+    EXPECT_ACTION("ScheduledActionActivateSyncTree", client_, 2, 5);
+    EXPECT_ACTION("ScheduledActionAnimate", client_, 3, 5);
+    EXPECT_ACTION("ScheduledActionDrawAndSwapIfPossible", client_, 4, 5);
+  }
+}
+
+TEST_F(SchedulerTest, DontSkipImplFrameIfCommitEstimateTooLong) {
+  scheduler_settings_.use_external_begin_frame_source = true;
+  SetUpScheduler(true);
+  fake_compositor_timing_history_->SetAllEstimatesTo(base::TimeDelta());
+  fake_compositor_timing_history_->SetBeginMainFrameToCommitDurationEstimate(
+      base::TimeDelta::FromMilliseconds(16));
+  EXPECT_SCOPED(ImplFrameInHighLatencyDontSkipImplFrame());
+}
+
+TEST_F(SchedulerTest, DontSkipImplFrameIfReadyToActivateEstimateTooLong) {
+  scheduler_settings_.use_external_begin_frame_source = true;
+  SetUpScheduler(true);
+  fake_compositor_timing_history_->SetAllEstimatesTo(base::TimeDelta());
+  fake_compositor_timing_history_->SetCommitToReadyToActivateDurationEstimate(
+      base::TimeDelta::FromMilliseconds(16));
+  EXPECT_SCOPED(ImplFrameInHighLatencyDontSkipImplFrame());
+}
+
+TEST_F(SchedulerTest, DontSkipImplFrameIfActivateEstimateTooLong) {
+  scheduler_settings_.use_external_begin_frame_source = true;
+  SetUpScheduler(true);
+  fake_compositor_timing_history_->SetAllEstimatesTo(base::TimeDelta());
+  fake_compositor_timing_history_->SetActivateDurationEstimate(
+      base::TimeDelta::FromMilliseconds(16));
+  EXPECT_SCOPED(ImplFrameInHighLatencyDontSkipImplFrame());
+}
+
+TEST_F(SchedulerTest, DontSkipImplFrameIfDrawEstimateTooLong) {
+  scheduler_settings_.use_external_begin_frame_source = true;
+  SetUpScheduler(true);
+  fake_compositor_timing_history_->SetAllEstimatesTo(base::TimeDelta());
+  fake_compositor_timing_history_->SetDrawDurationEstimate(
+      base::TimeDelta::FromMilliseconds(16));
+  EXPECT_SCOPED(ImplFrameInHighLatencyDontSkipImplFrame());
+}
+
+TEST_F(SchedulerTest, MainAndSwapInHighLatencyMode) {
+  // Set up client with custom estimates.
+  // This test starts off with expensive estimates to prevent latency recovery
+  // initially, then lowers the estimates to enable it once both the main
+  // and impl threads are in a high latency mode.
+  scheduler_settings_.use_external_begin_frame_source = true;
+  SetUpScheduler(true);
+
+  auto slow_duration = base::TimeDelta::FromMilliseconds(16);
+  fake_compositor_timing_history_->SetAllEstimatesTo(base::TimeDelta());
+  fake_compositor_timing_history_->SetDrawDurationEstimate(slow_duration);
+
+  // To get into a high latency state, this test disables automatic swap acks.
+  scheduler_->SetMaxSwapsPending(1);
+  client_->SetAutomaticSwapAck(false);
+
+  // Impl thread hits deadline before commit finishes to make
+  // MainThreadIsInHighLatencyMode true
+  client_->Reset();
+  scheduler_->SetNeedsCommit();
+  EXPECT_FALSE(scheduler_->MainThreadIsInHighLatencyMode());
+  EXPECT_SCOPED(AdvanceFrame());
+  EXPECT_FALSE(scheduler_->MainThreadIsInHighLatencyMode());
+  task_runner().RunTasksWhile(client_->ImplFrameDeadlinePending(true));
+  EXPECT_TRUE(scheduler_->MainThreadIsInHighLatencyMode());
+  scheduler_->NotifyBeginMainFrameStarted();
+  scheduler_->NotifyReadyToCommit();
+  scheduler_->NotifyReadyToActivate();
+  EXPECT_TRUE(scheduler_->MainThreadIsInHighLatencyMode());
+
+  EXPECT_ACTION("SetNeedsBeginFrames(true)", client_, 0, 5);
+  EXPECT_ACTION("WillBeginImplFrame", client_, 1, 5);
+  EXPECT_ACTION("ScheduledActionSendBeginMainFrame", client_, 2, 5);
+  EXPECT_ACTION("ScheduledActionCommit", client_, 3, 5);
+  EXPECT_ACTION("ScheduledActionActivateSyncTree", client_, 4, 5);
+
+  // Draw and swap for first commit, start second commit.
+  client_->Reset();
+  scheduler_->SetNeedsCommit();
+  EXPECT_TRUE(scheduler_->MainThreadIsInHighLatencyMode());
+  EXPECT_SCOPED(AdvanceFrame());
+  EXPECT_TRUE(scheduler_->MainThreadIsInHighLatencyMode());
+  task_runner().RunTasksWhile(client_->ImplFrameDeadlinePending(true));
+  scheduler_->NotifyBeginMainFrameStarted();
+  scheduler_->NotifyReadyToCommit();
+  scheduler_->NotifyReadyToActivate();
+
+  EXPECT_ACTION("WillBeginImplFrame", client_, 0, 6);
+  EXPECT_ACTION("ScheduledActionAnimate", client_, 1, 6);
+  EXPECT_ACTION("ScheduledActionSendBeginMainFrame", client_, 2, 6);
+  EXPECT_ACTION("ScheduledActionDrawAndSwapIfPossible", client_, 3, 6);
+  EXPECT_ACTION("ScheduledActionCommit", client_, 4, 6);
+  EXPECT_ACTION("ScheduledActionActivateSyncTree", client_, 5, 6);
+
+  // Don't call scheduler_->DidSwapBuffersComplete() until after next frame
+  // to put the impl thread in a high latency mode.
+  client_->Reset();
+  scheduler_->SetNeedsCommit();
+  EXPECT_TRUE(scheduler_->MainThreadIsInHighLatencyMode());
+  EXPECT_SCOPED(AdvanceFrame());
+  EXPECT_TRUE(scheduler_->MainThreadIsInHighLatencyMode());
+  task_runner().RunTasksWhile(client_->ImplFrameDeadlinePending(true));
+  scheduler_->DidSwapBuffersComplete();
+
+  EXPECT_ACTION("WillBeginImplFrame", client_, 0, 2);
+  EXPECT_ACTION("ScheduledActionAnimate", client_, 1, 2);
+  // Note: BeginMainFrame and swap are skipped here because of
+  // swap ack backpressure, not because of latency recovery.
+  EXPECT_FALSE(client_->HasAction("ScheduledActionSendBeginMainFrame"));
+  EXPECT_FALSE(client_->HasAction("ScheduledActionDrawAndSwapIfPossible"));
+
+  // Lower estimates so that the scheduler will attempt latency recovery.
+  auto fast_duration = base::TimeDelta::FromMilliseconds(1);
+  fake_compositor_timing_history_->SetAllEstimatesTo(fast_duration);
+
+  // Now that both threads are in a high latency mode, make sure we
+  // skip the BeginMainFrame, then the BeginImplFrame, but not both
+  // at the same time.
+
+  // Verify we skip BeginMainFrame first.
+  client_->Reset();
+  // Previous commit request is still outstanding.
+  EXPECT_TRUE(scheduler_->NeedsCommit());
+  EXPECT_TRUE(scheduler_->MainThreadIsInHighLatencyMode());
+  SendNextBeginFrame();
+  task_runner().RunTasksWhile(client_->ImplFrameDeadlinePending(true));
+  EXPECT_FALSE(scheduler_->MainThreadIsInHighLatencyMode());
+
+  EXPECT_ACTION("WillBeginImplFrame", client_, 0, 3);
+  EXPECT_ACTION("ScheduledActionAnimate", client_, 1, 3);
+  EXPECT_ACTION("ScheduledActionDrawAndSwapIfPossible", client_, 2, 3);
+  EXPECT_FALSE(client_->HasAction("ScheduledActionSendBeginMainFrame"));
+
+  // Verify we skip the BeginImplFrame second.
+  client_->Reset();
+  // Previous commit request is still outstanding.
+  EXPECT_TRUE(scheduler_->NeedsCommit());
+  EXPECT_FALSE(scheduler_->MainThreadIsInHighLatencyMode());
+  SendNextBeginFrame();
+  task_runner().RunTasksWhile(client_->ImplFrameDeadlinePending(true));
+  EXPECT_FALSE(scheduler_->MainThreadIsInHighLatencyMode());
+  scheduler_->DidSwapBuffersComplete();
+  EXPECT_FALSE(scheduler_->MainThreadIsInHighLatencyMode());
+
+  EXPECT_NO_ACTION(client_);
+
+  // Then verify we operate in a low latency mode.
+  client_->Reset();
+  // Previous commit request is still outstanding.
+  EXPECT_TRUE(scheduler_->NeedsCommit());
+  EXPECT_FALSE(scheduler_->MainThreadIsInHighLatencyMode());
+  SendNextBeginFrame();
+  EXPECT_FALSE(scheduler_->MainThreadIsInHighLatencyMode());
+  scheduler_->NotifyBeginMainFrameStarted();
+  scheduler_->NotifyReadyToCommit();
+  scheduler_->NotifyReadyToActivate();
+  task_runner().RunTasksWhile(client_->ImplFrameDeadlinePending(true));
+  EXPECT_FALSE(scheduler_->MainThreadIsInHighLatencyMode());
+  scheduler_->DidSwapBuffersComplete();
+  EXPECT_FALSE(scheduler_->MainThreadIsInHighLatencyMode());
+
+  EXPECT_ACTION("WillBeginImplFrame", client_, 0, 6);
+  EXPECT_ACTION("ScheduledActionSendBeginMainFrame", client_, 1, 6);
+  EXPECT_ACTION("ScheduledActionCommit", client_, 2, 6);
+  EXPECT_ACTION("ScheduledActionActivateSyncTree", client_, 3, 6);
+  EXPECT_ACTION("ScheduledActionAnimate", client_, 4, 6);
+  EXPECT_ACTION("ScheduledActionDrawAndSwapIfPossible", client_, 5, 6);
 }
 
 TEST_F(
     SchedulerTest,
     Deadlock_CommitMakesProgressWhileSwapTrottledAndActiveTreeNeedsFirstDraw) {
   // NPAPI plugins on Windows block the Browser UI thread on the Renderer main
   // thread. This prevents the scheduler from receiving any pending swap acks.
 
   // Since we are simulating a long commit, set up a client with draw duration
   // estimates that prevent skipping main frames to get to low latency mode.
@@ skipping 1586 matching lines @@
   scheduler_->SetImplLatencyTakesPriority(true);
   scheduler_->SetChildrenNeedBeginFrames(true);
 
   EXPECT_SCOPED(AdvanceFrame());
   EXPECT_TRUE(client_->begin_frame_is_sent_to_children());
   EXPECT_FALSE(client_->begin_frame_args_sent_to_children().on_critical_path);
 }
 
 }  // namespace
 }  // namespace cc