cc: Making BeginFrameSources support multiple BeginFrameObservers.

cc/scheduler/scheduler.h

Index: cc/scheduler/scheduler.h
diff --git a/cc/scheduler/scheduler.h b/cc/scheduler/scheduler.h
index 8ed584a5d49a7c6492eeef1e37043c538e1d7ecd..6cf7dcf77c1df33475486d7cf857cd13dc4d348f 100644
--- a/cc/scheduler/scheduler.h
+++ b/cc/scheduler/scheduler.h
@@ -157,8 +157,8 @@ class CC_EXPORT Scheduler : public BeginFrameObserverMixIn {
 
   void SetDeferCommits(bool defer_commits);
 
-  scoped_refptr<base::trace_event::ConvertableToTraceFormat> AsValue() const;
-  void AsValueInto(base::trace_event::TracedValue* value) const override;
+  scoped_refptr<base::trace_event::ConvertableToTraceFormat> AsValue();
+  void AsValueInto(base::trace_event::TracedValue* value) override;
 
   void SetContinuousPainting(bool continuous_painting) {
     state_machine_.SetContinuousPainting(continuous_painting);
@@ -224,7 +224,7 @@ class CC_EXPORT Scheduler : public BeginFrameObserverMixIn {
   void SetupPollingMechanisms();
   void DrawAndSwapIfPossible();
   void ProcessScheduledActions();
-  bool CanCommitAndActivateBeforeDeadline() const;
+  bool CanCommitAndActivateBeforeDeadline();
   void AdvanceCommitStateIfPossible();
   bool IsBeginMainFrameSentOrStarted() const;
   void BeginRetroFrame();