Revert 266822 "Remove dropped frame counting and task posting fr..."

trunk/src/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 and
-// dispatching callbacks when detecting changes in video frames.
+// VideoFrameCompositor handles incoming frames by notifying the compositor in a
+// thread-safe manner.
 //
-// Typical usage is to deliver ready-to-be-displayed video frames to
+// Typical usage is to deliver the output of VideoRendererImpl to
 // UpdateCurrentFrame() so that VideoFrameCompositor can take care of tracking
-// changes in video frames and firing callbacks as needed.
+// dropped frames and firing callbacks as needed.
 //
-// While VideoFrameCompositor must live on the same thread as the compositor,
-// GetCurrentFrame() is callable from any thread to let clients access the
-// current frame for non-compositing purposes.
-class CONTENT_EXPORT VideoFrameCompositor
-    : NON_EXPORTED_BASE(public cc::VideoFrameProvider) {
+// All APIs are callable from any thread.
+class CONTENT_EXPORT VideoFrameCompositor {
  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);
-  virtual ~VideoFrameCompositor();
+  ~VideoFrameCompositor();
 
-  // 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;
+  cc::VideoFrameProvider* GetVideoFrameProvider();
 
   // 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();
+
+  // Returns the number of frames dropped before the compositor was notified
+  // of a new frame.
+  uint32 GetFramesDroppedBeforeCompositorWasNotified();
+
+  void SetFramesDroppedBeforeCompositorWasNotifiedForTesting(
+      uint32 dropped_frames);
+
  private:
-  base::Callback<void(gfx::Size)> natural_size_changed_cb_;
-  base::Callback<void(bool)> opacity_changed_cb_;
-
-  cc::VideoFrameProvider::Client* client_;
-
-  base::Lock lock_;
-  scoped_refptr<media::VideoFrame> current_frame_;
+  class Internal;
+  Internal* internal_;
 
   DISALLOW_COPY_AND_ASSIGN(VideoFrameCompositor);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_RENDERER_MEDIA_VIDEO_FRAME_COMPOSITOR_H_