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

cc/scheduler/scheduler.h

 // 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.
 
 #ifndef CC_SCHEDULER_SCHEDULER_H_
 #define CC_SCHEDULER_SCHEDULER_H_
 
 #include <deque>
 #include <string>
 
@@ skipping 81 matching lines @@
   void SetNeedsRedraw();
 
   void SetNeedsAnimate();
 
   void SetNeedsPrepareTiles();
 
   void SetMaxSwapsPending(int max);
   void DidSwapBuffers();
   void DidSwapBuffersComplete();
 
-  void SetImplLatencyTakesPriority(bool impl_latency_takes_priority);
+  void SetSmoothnessMode(bool smoothness_takes_priority,

[Sami, 2015/11/06 11:54:42]

nit: some of the (test) call sites might read a bit better if this was split
into two setters. The naming is also a little confusing now since
|smoothness_takes_priority| only sometimes makes impl take priority :)

How about something like this:

SetImplLatencyIsImportant(...)
SetBestEffortMainSynchronizationEnabled(scroll_affects_scroll_handler)  // Later
we'd likely add rAF and CSS animation bits here.

Not totally happy with the naming but WDYT of the general idea?

[brianderson, 2015/11/12 20:22:04]

That sounds good. I might call the second one SetScrollAffectsScrollHandler, and
change the name again in the follow up patches.

+                         bool scroll_affects_scroll_handler);
 
   void NotifyReadyToCommit();
   void BeginMainFrameAborted(CommitEarlyOutReason reason);
   void DidCommit();
 
   void WillPrepareTiles();
   void DidPrepareTiles();
   void DidLoseOutputSurface();
   void DidCreateAndInitializeOutputSurface();
 
   // Tests do not want to shut down until all possible BeginMainFrames have
   // occured to prevent flakiness.
   bool MainFrameForTestingWillHappen() const {
     return state_machine_.CommitPending() ||
            state_machine_.CouldSendBeginMainFrame();
   }
 
   bool CommitPending() const { return state_machine_.CommitPending(); }
   bool RedrawPending() const { return state_machine_.RedrawPending(); }
   bool PrepareTilesPending() const {
     return state_machine_.PrepareTilesPending();
   }
   bool BeginImplFrameDeadlinePending() const {
     return !begin_impl_frame_deadline_task_.IsCancelled();
   }
   bool ImplLatencyTakesPriority() const {
-    return state_machine_.impl_latency_takes_priority();
+    return state_machine_.ImplLatencyTakesPriority();
   }
 
   // Pass in a main_thread_start_time of base::TimeTicks() if it is not
   // known or not trustworthy (e.g. blink is running on a remote channel)
   // to signal that the start time isn't known and should not be used for
   // scheduling or statistics purposes.
   void NotifyBeginMainFrameStarted(base::TimeTicks main_thread_start_time);
 
   base::TimeTicks LastBeginImplFrameTime();
 
@@ skipping 54 matching lines @@
 
  private:
   void ScheduleBeginImplFrameDeadline();
   void ScheduleBeginImplFrameDeadlineIfNeeded();
   void SetupNextBeginFrameIfNeeded();
   void PostBeginRetroFrameIfNeeded();
   void DrawAndSwapIfPossible();
   void DrawAndSwapForced();
   void ProcessScheduledActions();
   void UpdateCompositorTimingHistoryRecordingEnabled();
-  bool ShouldRecoverMainLatency(const BeginFrameArgs& args) const;
-  bool ShouldRecoverImplLatency(const BeginFrameArgs& args) const;
-  bool CanCommitAndActivateBeforeDeadline(const BeginFrameArgs& args) const;
+  bool ShouldRecoverMainLatency(const BeginFrameArgs& args,
+                                bool can_activate_before_deadline) const;
+  bool ShouldRecoverImplLatency(const BeginFrameArgs& args,
+                                bool can_activate_before_deadline) const;
+  bool CanCommitAndActivateBeforeDeadline(
+      const BeginFrameArgs& args,
+      base::TimeDelta bmf_to_activate_estimate) const;
   void AdvanceCommitStateIfPossible();
   bool IsBeginMainFrameSentOrStarted() const;
   void BeginRetroFrame();
   void BeginImplFrameWithDeadline(const BeginFrameArgs& args);
   void BeginImplFrameSynchronous(const BeginFrameArgs& args);
   void BeginImplFrame(const BeginFrameArgs& args);
   void FinishImplFrame();
   void OnBeginImplFrameDeadline();
   void PollToAdvanceCommitState();
 
@@ skipping 14 matching lines @@
   }
 
   base::WeakPtrFactory<Scheduler> weak_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(Scheduler);
 };
 
 }  // namespace cc
 
 #endif  // CC_SCHEDULER_SCHEDULER_H_