cc: Don't attempt main thread synchronization if it is slow.

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 "base/trace_event/trace_event.h"
 #include "cc/scheduler/scheduler.h"
 #include "cc/test/begin_frame_args_test.h"
 #include "testing/gtest/include/gtest/gtest.h"
@@ skipping 1883 matching lines @@
   state.SetNeedsBeginMainFrame();
   state.OnBeginImplFrame();
   EXPECT_ACTION_UPDATE_STATE(SchedulerStateMachine::ACTION_ANIMATE);
   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.SetImplLatencyTakesPriority(true);
+  state.SetTreePrioritiesAndScrollState(
+      SMOOTHNESS_TAKES_PRIORITY,
+      ScrollHandlerState::SCROLL_DOES_NOT_AFFECT_SCROLL_HANDLER);
   EXPECT_TRUE(state.ShouldTriggerBeginImplFrameDeadlineImmediately());
 
   // 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();
 
@@ skipping 214 matching lines @@
   EXPECT_FALSE(state.ProactiveBeginFrameWanted());
   bool commit_has_no_updates = true;
   state.WillCommit(commit_has_no_updates);
   EXPECT_TRUE(state.ProactiveBeginFrameWanted());
   state.OnBeginImplFrame();
   EXPECT_FALSE(state.ProactiveBeginFrameWanted());
 }
 
 }  // namespace
 }  // namespace cc