cc: Create ProxyBeginFrameSource

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 148 matching lines @@
   // needs_begin_frames change.
   virtual void OnNeedsBeginFramesChange(bool needs_begin_frames) {}
 
   BeginFrameObserver* observer_;
   bool needs_begin_frames_;
 
  private:
   bool inside_as_value_into_;
 };
 
+class CC_EXPORT ProxyBeginFrameSource : public BeginFrameSource {

[mithro-old, 2015/03/23 11:32:17]

If I understand correctly, this just takes a message from a BeginFrameSource and
forwards it to multiple observers?

[simonhong, 2015/03/23 11:46:39]

Yes, right.

+ public:
+  class Delegate {
+   public:
+    virtual void SetChildrenNeedBeginFrames(bool needs_begin_frames) = 0;
+  };
+
+  ProxyBeginFrameSource();
+  ~ProxyBeginFrameSource() override;
+
+  // BeginFrameSource
+  bool NeedsBeginFrames() const override;
+  // SetNeedsBeginFrames() is not used for now.
+  // Instead, turning BeginFrame on/off is controlled by Add/RemoveObserver.

[mithro-old, 2015/03/23 11:32:17]

I think this violates the BeginFrameSource interface, if
SetNeedsBeginFrames(false) is called, we shouldn't be sending any more
BeginFrames?

Can you explain why you are controlling this via Observers rather than the
normal method?

[simonhong, 2015/03/23 11:46:39]

This is special login for ProxyBeginFrameSource.
We only can stop sending BeginFrame if there is no observer.
Of course, login in Add/RemoveObserver can be moved into SetNeedsBeginFrames().

+  void SetNeedsBeginFrames(bool needs_begin_frames) override {}
+  void DidFinishFrame(size_t remaining_frames) override {}
+  void AddObserver(BeginFrameObserver* obs) override;
+  void RemoveObserver(BeginFrameObserver* obs) override;
+  void SetClientReady() override {}
+  void AsValueInto(base::debug::TracedValue* dict) const override;
+
+  void set_delegate(Delegate* delegate) {

[mithro-old, 2015/03/23 11:32:17]

Why is this set_delegate rather than SetDelegate?

[simonhong, 2015/03/23 11:46:39]

As I know, this style is used for just get/set method.
Am I wrong? :)

+    delegate_ = delegate;
+  }
+
+  // virtual for testing.
+  virtual void BeginFrames(const BeginFrameArgs& args);
+
+ private:
+  Delegate* delegate_;  // Not owned.
+  // Used to send to any new BeginFrameObserver immediately.
+  BeginFrameArgs missed_begin_frame_args_;
+  ObserverList<BeginFrameObserver> observer_list_;
+
+  DISALLOW_COPY_AND_ASSIGN(ProxyBeginFrameSource);
+};
+
+
 // A frame source which calls BeginFrame (at the next possible time) as soon as
 // remaining frames reaches zero.
 class CC_EXPORT BackToBackBeginFrameSource : public BeginFrameSourceMixIn {
  public:
   static scoped_ptr<BackToBackBeginFrameSource> Create(
       base::SingleThreadTaskRunner* task_runner);
   ~BackToBackBeginFrameSource() override;
 
   // BeginFrameSource
   void DidFinishFrame(size_t remaining_frames) override;
@@ skipping 97 matching lines @@
 
   base::TimeDelta minimum_interval_;
 
   BeginFrameSource* active_source_;
   std::set<BeginFrameSource*> source_list_;
 };
 
 }  // namespace cc
 
 #endif  // CC_SCHEDULER_BEGIN_FRAME_SOURCE_H_