Remove dropped frame counting and task posting from VideoFrameCompositor.

content/renderer/media/video_frame_compositor.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 CONTENT_RENDERER_MEDIA_VIDEO_FRAME_COMPOSITOR_H_
 #define CONTENT_RENDERER_MEDIA_VIDEO_FRAME_COMPOSITOR_H_
 
 #include "base/callback.h"
 #include "base/memory/ref_counted.h"
 #include "base/synchronization/lock.h"
+#include "cc/layers/video_frame_provider.h"
 #include "content/common/content_export.h"
 #include "ui/gfx/size.h"
 
-namespace base {
-class SingleThreadTaskRunner;
-}
-
-namespace cc {
-class VideoFrameProvider;
-}
-
 namespace media {
 class VideoFrame;
 }
 
 namespace content {
 
-// VideoFrameCompositor handles incoming frames by notifying the compositor in a
-// thread-safe manner.
+// VideoFrameCompositor handles incoming frames by notifying the compositor and
+// dispatching callbacks when detecting changes in video frames.
 //
-// Typical usage is to deliver the output of VideoRendererImpl to
+// Typical usage is to deliver ready-to-be-displayed video frames to
 // UpdateCurrentFrame() so that VideoFrameCompositor can take care of tracking
-// dropped frames and firing callbacks as needed.
+// changes in video frames and firing callbacks as needed.
 //
-// All APIs are callable from any thread.
-class CONTENT_EXPORT VideoFrameCompositor {
+// VideoFrameCompositor must live on the same thread as the compositor.

[xhwang, 2014/04/28 06:42:59]

Can you add more comments about threading? It seems VFC must live on a single
thread (the compositor thread), but you have a |lock_| to protect the
|current_frame_|.

[scherkus (not reviewing), 2014/04/28 16:59:47]

Done.

+class CONTENT_EXPORT VideoFrameCompositor : public cc::VideoFrameProvider {
  public:
-  // |compositor_task_runner| is the task runner of the compositor.
-  //
   // |natural_size_changed_cb| is run with the new natural size of the video
   // frame whenever a change in natural size is detected. It is not called the
   // first time UpdateCurrentFrame() is called. Run on the same thread as the
   // caller of UpdateCurrentFrame().
   //
   // |opacity_changed_cb| is run when a change in opacity is detected. It *is*
   // called the first time UpdateCurrentFrame() is called. Run on the same
   // thread as the caller of UpdateCurrentFrame().
   //
   // TODO(scherkus): Investigate the inconsistency between the callbacks with
   // respect to why we don't call |natural_size_changed_cb| on the first frame.
   // I suspect it was for historical reasons that no longer make sense.
   VideoFrameCompositor(
-      const scoped_refptr<base::SingleThreadTaskRunner>& compositor_task_runner,
       const base::Callback<void(gfx::Size)>& natural_size_changed_cb,
       const base::Callback<void(bool)>& opacity_changed_cb);
-  ~VideoFrameCompositor();
+  virtual ~VideoFrameCompositor();
 
-  cc::VideoFrameProvider* GetVideoFrameProvider();
+  // cc::VideoFrameProvider implementation.
+  //
+  // NOTE: GetCurrentFrame() is safe to call from any thread.
+  virtual void SetVideoFrameProviderClient(
+      cc::VideoFrameProvider::Client* client) OVERRIDE;
+  virtual scoped_refptr<media::VideoFrame> GetCurrentFrame() OVERRIDE;
+  virtual void PutCurrentFrame(
+      const scoped_refptr<media::VideoFrame>& frame) OVERRIDE;
 
   // Updates the current frame and notifies the compositor.
   void UpdateCurrentFrame(const scoped_refptr<media::VideoFrame>& frame);
 
-  // Retrieves the last frame set via UpdateCurrentFrame() for non-compositing
-  // purposes (e.g., painting to a canvas).
-  //
-  // Note that the compositor retrieves frames via the cc::VideoFrameProvider
-  // interface instead of using this method.
-  scoped_refptr<media::VideoFrame> GetCurrentFrame();
+ private:
+  base::Callback<void(gfx::Size)> natural_size_changed_cb_;
+  base::Callback<void(bool)> opacity_changed_cb_;
 
-  // Returns the number of frames dropped before the compositor was notified
-  // of a new frame.
-  uint32 GetFramesDroppedBeforeCompositorWasNotified();
+  cc::VideoFrameProvider::Client* client_;
 
-  void SetFramesDroppedBeforeCompositorWasNotifiedForTesting(
-      uint32 dropped_frames);
-
- private:
-  class Internal;
-  Internal* internal_;
+  base::Lock lock_;
+  scoped_refptr<media::VideoFrame> current_frame_;
 
   DISALLOW_COPY_AND_ASSIGN(VideoFrameCompositor);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_RENDERER_MEDIA_VIDEO_FRAME_COMPOSITOR_H_