cc: Making BeginFrameSources support multiple BeginFrameObservers.

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 <set>
 #include <string>
 
@@ skipping 118 matching lines @@
 
 // Simple base class which implements a BeginFrameSource.
 // Implementation classes should:
 //  - Implement the pure virtual (Set)NeedsBeginFrames methods from
 //    BeginFrameSource.
 //  - Use the CallOnBeginFrame method to call to the observer(s).
 //  - Recommended (but not required) to call BeginFrameSourceBase::AsValueInto
 //    in their own AsValueInto implementation.
 class CC_EXPORT BeginFrameSourceBase : public BeginFrameSource {
  public:
-  ~BeginFrameSourceBase() override {}
+  ~BeginFrameSourceBase() override;
 
   // BeginFrameSource
   bool NeedsBeginFrames() const final;
   void SetNeedsBeginFrames(bool needs_begin_frames) final;
   void DidFinishFrame(size_t remaining_frames) override {}
   void AddObserver(BeginFrameObserver* obs) final;
   void RemoveObserver(BeginFrameObserver* obs) final;
   void SetClientReady() override {}
 
   // Tracing support - Recommend (but not required) to call this implementation
   // in any override.
   void AsValueInto(base::trace_event::TracedValue* dict) const override;
 
  protected:
   BeginFrameSourceBase();
 
   // These methods should be used by subclasses to make the call to the
   // observers.
   void CallOnBeginFrame(const BeginFrameArgs& args);
 
   // This method should be overridden if you want to change some behaviour on
   // needs_begin_frames change.
   virtual void OnNeedsBeginFramesChange(bool needs_begin_frames) {}
 
-  BeginFrameObserver* observer_;
+  base::ObserverList<const BeginFrameObserver>::Iterator
+  getConstObserverListIterator() const;
+  base::ObserverList<BeginFrameObserver> observer_list_;
   bool needs_begin_frames_;
 
  private:
   bool inside_as_value_into_;
 
   DISALLOW_COPY_AND_ASSIGN(BeginFrameSourceBase);
 };
 
 // A frame source which calls BeginFrame (at the next possible time) as soon as
 // remaining frames reaches zero.
@@ skipping 108 matching lines @@
   BeginFrameSource* active_source_;
   std::set<BeginFrameSource*> source_list_;
 
  private:
   DISALLOW_COPY_AND_ASSIGN(BeginFrameSourceMultiplexer);
 };
 
 }  // namespace cc
 
 #endif  // CC_SCHEDULER_BEGIN_FRAME_SOURCE_H_