cc: Make separate interface for BeginFrame ipc from OutputSurface

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>
 
 #include "base/debug/trace_event.h"
 #include "base/logging.h"
+#include "base/memory/ref_counted.h"
 #include "cc/output/begin_frame_args.h"
 #include "cc/output/vsync_parameter_observer.h"
 #include "cc/scheduler/delay_based_time_source.h"
 
 namespace cc {
 
 // (Pure) Interface for observing BeginFrame messages from BeginFrameSource
 // objects.
 class CC_EXPORT BeginFrameObserver {
  public:
@@ skipping 132 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_;
 };
 
+// A frame source that delivers BeginFrame from outside of cc.
+// ExternalBeginFrameSource is ref-counted object because it could be used by
+// outside of cc to deliver new BeginFrame.
+class CC_EXPORT ExternalBeginFrameSource
+    : public BeginFrameSourceMixIn,
+      public base::RefCounted<ExternalBeginFrameSource>,
+      public NON_EXPORTED_BASE(base::NonThreadSafe) {
+ public:
+  ExternalBeginFrameSource() {}
+
+  // Tells the Source that client is ready to handle external BeginFrames.
+  virtual void SetClientReady() {}
+
+ protected:
+  friend class base::RefCounted<ExternalBeginFrameSource>;
+  virtual ~ExternalBeginFrameSource() {}
+
+ private:
+  DISALLOW_COPY_AND_ASSIGN(ExternalBeginFrameSource);
+};
+
 // 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);
   virtual ~BackToBackBeginFrameSource();
 
   // BeginFrameSource
   virtual void DidFinishFrame(size_t remaining_frames) override;
@@ skipping 96 matching lines @@
 
   base::TimeDelta minimum_interval_;
 
   BeginFrameSource* active_source_;
   std::set<BeginFrameSource*> source_list_;
 };
 
 }  // namespace cc
 
 #endif  // CC_SCHEDULER_BEGIN_FRAME_SOURCE_H_