Make disable vsync run the renderer independently

cc/scheduler/begin_frame_source.h

 // Copyright 2014 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_BEGIN_FRAME_SOURCE_H_
 #define CC_SCHEDULER_BEGIN_FRAME_SOURCE_H_
 
 #include <stddef.h>
 #include <stdint.h>
 
@@ skipping 94 matching lines @@
   // processing (rather than toggling SetNeedsBeginFrames every frame). It is
   // used by systems like the BackToBackFrameSource to make sure only one frame
   // is pending at a time.
   virtual void DidFinishFrame(BeginFrameObserver* obs,
                               size_t remaining_frames) = 0;
 
   // Add/Remove an observer from the source. When no observers are added the BFS
   // should shut down its timers, disable vsync, etc.
   virtual void AddObserver(BeginFrameObserver* obs) = 0;
   virtual void RemoveObserver(BeginFrameObserver* obs) = 0;
+
+  // Returns false if the begin frame source will just continue to produce
+  // begin frames without waiting.
+  virtual bool IsThrottled() const = 0;
 };
 
 // A BeginFrameSource that does nothing.
-class StubBeginFrameSource : public BeginFrameSource {
+class CC_EXPORT StubBeginFrameSource : public BeginFrameSource {
  public:
   void DidFinishFrame(BeginFrameObserver* obs,
                       size_t remaining_frames) override {}
   void AddObserver(BeginFrameObserver* obs) override {}
   void RemoveObserver(BeginFrameObserver* obs) override {}
+  bool IsThrottled() const override;
 };
 
 // A frame source which ticks itself independently.
 class CC_EXPORT SyntheticBeginFrameSource : public BeginFrameSource {
  public:
   ~SyntheticBeginFrameSource() override;
 
   virtual void OnUpdateVSyncParameters(base::TimeTicks timebase,
                                        base::TimeDelta interval) = 0;
   // This overrides any past or future interval from updating vsync parameters.
   virtual void SetAuthoritativeVSyncInterval(base::TimeDelta interval) = 0;
 };
 
 // A frame source which calls BeginFrame (at the next possible time) as soon as
 // remaining frames reaches zero.
 class CC_EXPORT BackToBackBeginFrameSource : public SyntheticBeginFrameSource,
                                              public DelayBasedTimeSourceClient {
  public:
   explicit BackToBackBeginFrameSource(
       std::unique_ptr<DelayBasedTimeSource> time_source);
   ~BackToBackBeginFrameSource() override;
 
   // BeginFrameSource implementation.
   void AddObserver(BeginFrameObserver* obs) override;
   void RemoveObserver(BeginFrameObserver* obs) override;
   void DidFinishFrame(BeginFrameObserver* obs,
                       size_t remaining_frames) override;
+  bool IsThrottled() const override;
 
   // SyntheticBeginFrameSource implementation.
   void OnUpdateVSyncParameters(base::TimeTicks timebase,
                                base::TimeDelta interval) override {}
   void SetAuthoritativeVSyncInterval(base::TimeDelta interval) override {}
 
   // DelayBasedTimeSourceClient implementation.
   void OnTimerTick() override;
 
  private:
@@ skipping 12 matching lines @@
  public:
   explicit DelayBasedBeginFrameSource(
       std::unique_ptr<DelayBasedTimeSource> time_source);
   ~DelayBasedBeginFrameSource() override;
 
   // BeginFrameSource implementation.
   void AddObserver(BeginFrameObserver* obs) override;
   void RemoveObserver(BeginFrameObserver* obs) override;
   void DidFinishFrame(BeginFrameObserver* obs,
                       size_t remaining_frames) override {}
+  bool IsThrottled() const override;
 
   // SyntheticBeginFrameSource implementation.
   void OnUpdateVSyncParameters(base::TimeTicks timebase,
                                base::TimeDelta interval) override;
   void SetAuthoritativeVSyncInterval(base::TimeDelta interval) override;
 
   // DelayBasedTimeSourceClient implementation.
   void OnTimerTick() override;
 
  private:
@@ skipping 22 matching lines @@
  public:
   // Client lifetime must be preserved by owner past the lifetime of this class.
   explicit ExternalBeginFrameSource(ExternalBeginFrameSourceClient* client);
   ~ExternalBeginFrameSource() override;
 
   // BeginFrameSource implementation.
   void AddObserver(BeginFrameObserver* obs) override;
   void RemoveObserver(BeginFrameObserver* obs) override;
   void DidFinishFrame(BeginFrameObserver* obs,
                       size_t remaining_frames) override {}
+  bool IsThrottled() const override;
 
   void OnSetBeginFrameSourcePaused(bool paused);
   void OnBeginFrame(const BeginFrameArgs& args);
 
  protected:
   BeginFrameArgs missed_begin_frame_args_;
   std::unordered_set<BeginFrameObserver*> observers_;
   ExternalBeginFrameSourceClient* client_;
   bool paused_ = false;
 
  private:
   DISALLOW_COPY_AND_ASSIGN(ExternalBeginFrameSource);
 };
 
 }  // namespace cc
 
 #endif  // CC_SCHEDULER_BEGIN_FRAME_SOURCE_H_