Merge 277109 "cc: Don't swap throttle BeginMainFrame just after ..."

> cc: Don't swap throttle BeginMainFrame just after swapping
> 
> This will better reflect behavior prior to the
> OutputSurface+Scheduler refactor and will
> prevent us from skipping BeginMainFrames that
> the scheduler only meant to defer.
> 
> BUG=381346
> 
> Review URL: https://codereview.chromium.org/325303002

TBR=brianderson@chromium.org

Review URL: https://codereview.chromium.org/341083009

git-svn-id: svn://svn.chromium.org/chrome/branches/1985/src@278545 0039d316-1c4b-4281-b951-d872f2087c98

2 files changed, 65 insertions, 5 deletions

diff --git a/cc/scheduler/scheduler_state_machine.cc b/cc/scheduler/scheduler_state_machine.cc
index 3ed18f6..9302a49 100644
--- a/cc/scheduler/scheduler_state_machine.cc
+++ b/cc/scheduler/scheduler_state_machine.cc
@@ -500,9 +500,12 @@ bool SchedulerStateMachine::ShouldSendBeginMainFrame() const {
   if (!HasInitializedOutputSurface())
     return false;
 
-  // SwapAck throttle the BeginMainFrames
+  // SwapAck throttle the BeginMainFrames unless we just swapped.
   // TODO(brianderson): Remove this restriction to improve throughput.
-  if (pending_swaps_ >= max_pending_swaps_)
+  bool just_swapped_in_deadline =
+      begin_impl_frame_state_ == BEGIN_IMPL_FRAME_STATE_INSIDE_DEADLINE &&
+      HasSwappedThisFrame();
+  if (pending_swaps_ >= max_pending_swaps_ && !just_swapped_in_deadline)
     return false;
 
   if (skip_begin_main_frame_to_reduce_latency_)
diff --git a/cc/scheduler/scheduler_state_machine_unittest.cc b/cc/scheduler/scheduler_state_machine_unittest.cc
index 067f019..5ec43ad 100644
--- a/cc/scheduler/scheduler_state_machine_unittest.cc
+++ b/cc/scheduler/scheduler_state_machine_unittest.cc
@@ -2032,7 +2032,32 @@ TEST(SchedulerStateMachineTest, TestTriggerDeadlineEarlyAfterAbortedCommit) {
   EXPECT_TRUE(state.ShouldTriggerBeginImplFrameDeadlineEarly());
 }
 
-TEST(SchedulerStateMachineTest, TestTriggerDeadlineEarlyForSmoothness) {
+void FinishPreviousCommitAndDrawWithoutExitingDeadline(
+    StateMachine* state_ptr) {
+  // Gross, but allows us to use macros below.
+  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_PENDING_TREE);
+  EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_NONE);
+
+  state.OnBeginImplFrame(BeginFrameArgs::CreateForTesting());
+  EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_ANIMATE);
+  EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_NONE);
+
+  EXPECT_TRUE(state.ShouldTriggerBeginImplFrameDeadlineEarly());
+  state.OnBeginImplFrameDeadline();
+  EXPECT_ACTION_UPDATE_STATE(
+      SchedulerStateMachine::ACTION_DRAW_AND_SWAP_IF_POSSIBLE);
+  state.DidSwapBuffers();
+}
+
+TEST(SchedulerStateMachineTest, TestSmoothnessTakesPriority) {
   SchedulerSettings settings;
   settings.impl_side_painting = true;
   StateMachine state(settings);
@@ -2044,18 +2069,50 @@ TEST(SchedulerStateMachineTest, TestTriggerDeadlineEarlyForSmoothness) {
 
   // This test ensures that impl-draws are prioritized over main thread updates
   // in prefer smoothness mode.
-  state.OnBeginImplFrame(BeginFrameArgs::CreateForTesting());
   state.SetNeedsRedraw(true);
   state.SetNeedsCommit();
+  state.OnBeginImplFrame(BeginFrameArgs::CreateForTesting());
   EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_ANIMATE);
   EXPECT_ACTION_UPDATE_STATE(
       SchedulerStateMachine::ACTION_SEND_BEGIN_MAIN_FRAME);
   EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_NONE);
 
-  // The deadline is not triggered early until we enter prefer smoothness mode.
+  // Verify the deadline is not triggered early until we enter
+  // prefer smoothness mode.
   EXPECT_FALSE(state.ShouldTriggerBeginImplFrameDeadlineEarly());
   state.SetSmoothnessTakesPriority(true);
   EXPECT_TRUE(state.ShouldTriggerBeginImplFrameDeadlineEarly());
+
+  // Trigger the deadline.
+  state.OnBeginImplFrameDeadline();
+  EXPECT_ACTION_UPDATE_STATE(
+      SchedulerStateMachine::ACTION_DRAW_AND_SWAP_IF_POSSIBLE);
+  state.DidSwapBuffers();
+  EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_NONE);
+  state.DidSwapBuffersComplete();
+
+  // Request a new commit and finish the previous one.
+  state.SetNeedsCommit();
+  FinishPreviousCommitAndDrawWithoutExitingDeadline(&state);
+  EXPECT_ACTION_UPDATE_STATE(
+      SchedulerStateMachine::ACTION_SEND_BEGIN_MAIN_FRAME);
+  EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_NONE);
+  state.DidSwapBuffersComplete();
+  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 swap throttled
+  // and did not just swap.
+  state.SetNeedsCommit();
+  EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_NONE);
+  state.OnBeginImplFrame(BeginFrameArgs::CreateForTesting());
+  EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_NONE);
+  EXPECT_FALSE(state.ShouldTriggerBeginImplFrameDeadlineEarly());
+  state.OnBeginImplFrameDeadline();
+  EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_NONE);
 }
 
 TEST(SchedulerStateMachineTest, TestSetNeedsAnimate) {