Speculative revert by sheriff

media/blink/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 MEDIA_BLINK_VIDEO_FRAME_COMPOSITOR_H_
 #define MEDIA_BLINK_VIDEO_FRAME_COMPOSITOR_H_
 
 #include "base/callback.h"
 #include "base/memory/ref_counted.h"
-#include "base/single_thread_task_runner.h"
-#include "base/synchronization/lock.h"
 #include "cc/layers/video_frame_provider.h"
 #include "media/base/media_export.h"
-#include "media/base/video_renderer_sink.h"
 #include "ui/gfx/geometry/size.h"
 
 namespace media {
 class VideoFrame;
 
-// VideoFrameCompositor acts as a bridge between the media and cc layers for
-// rendering video frames. I.e. a media::VideoRenderer will talk to this class
-// from the media side, while a cc::VideoFrameProvider::Client will talk to it
-// from the cc side.
+// VideoFrameCompositor handles incoming frames by notifying the compositor and
+// dispatching callbacks when detecting changes in video frames.
 //
-// This class is responsible for requesting new frames from a video renderer in
-// response to requests from the VFP::Client. Since the VFP::Client may stop
-// issuing requests in response to visibility changes it is also responsible for
-// ensuring the "freshness" of the current frame for programmatic frame
-// requests; e.g., Canvas.drawImage() requests
+// Typical usage is to deliver ready-to-be-displayed video frames to
+// UpdateCurrentFrame() so that VideoFrameCompositor can take care of tracking
+// changes in video frames and firing callbacks as needed.
 //
-// This class is also responsible for detecting frames dropped by the compositor
-// after rendering and signaling that information to a RenderCallback. It
-// detects frames not dropped by verifying each GetCurrentFrame() is followed
-// by a PutCurrentFrame() before the next UpdateCurrentFrame() call.
-//
-// VideoRenderSink::RenderCallback implementations must call Start() and Stop()
-// once new frames are expected or are no longer expected to be ready; this data
-// is relayed to the compositor to avoid extraneous callbacks.
-//
-// VideoFrameCompositor must live on the same thread as the compositor, though
-// it may be constructed on any thread.
+// VideoFrameCompositor must live on the same thread as the compositor.
 class MEDIA_EXPORT VideoFrameCompositor
-    : public VideoRendererSink,
-      NON_EXPORTED_BASE(public cc::VideoFrameProvider) {
+    : NON_EXPORTED_BASE(public cc::VideoFrameProvider) {
  public:
-  // |compositor_task_runner| is the task runner on which this class will live,
-  // though it may be constructed on any thread.
-  //
   // |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(dalecurtis): Investigate the inconsistency between the callbacks with
+  // 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);
-
-  // Destruction must happen on the compositor thread; Stop() must have been
-  // called before destruction starts.
   ~VideoFrameCompositor() override;
 
-  // Returns |current_frame_| if it was refreshed recently; otherwise, if
-  // |callback_| is available, requests a new frame and returns that one.
-  //
-  // This is required for programmatic frame requests where the compositor may
-  // have stopped issuing UpdateCurrentFrame() callbacks in response to
-  // visibility changes in the output layer.
-  scoped_refptr<VideoFrame> GetCurrentFrameAndUpdateIfStale();
-
-  // cc::VideoFrameProvider implementation. These methods must be called on the
-  // |compositor_task_runner_|.
+  // cc::VideoFrameProvider implementation.
   void SetVideoFrameProviderClient(
       cc::VideoFrameProvider::Client* client) override;
-  bool UpdateCurrentFrame(base::TimeTicks deadline_min,
-                          base::TimeTicks deadline_max) override;
   scoped_refptr<VideoFrame> GetCurrentFrame() override;
-  void PutCurrentFrame() override;
+  void PutCurrentFrame(const scoped_refptr<VideoFrame>& frame) override;
 
-  // VideoRendererSink implementation. These methods must be called from the
-  // same thread (typically the media thread).
-  void Start(RenderCallback* callback) override;
-  void Stop() override;
-  void PaintFrameUsingOldRenderingPath(
-      const scoped_refptr<VideoFrame>& frame) override;
+  // Updates the current frame and notifies the compositor.
+  void UpdateCurrentFrame(const scoped_refptr<VideoFrame>& frame);
 
  private:
-  // Called on the compositor thread to start or stop rendering if rendering was
-  // previously started or stopped before we had a |callback_|.
-  void OnRendererStateUpdate();
-
-  scoped_refptr<base::SingleThreadTaskRunner> compositor_task_runner_;
-
-  // These callbacks are executed on the compositor thread.
   base::Callback<void(gfx::Size)> natural_size_changed_cb_;
   base::Callback<void(bool)> opacity_changed_cb_;
 
-  // These values are only set and read on the compositor thread.
   cc::VideoFrameProvider::Client* client_;
+
   scoped_refptr<VideoFrame> current_frame_;
 
-  // These values are updated and read from the media and compositor threads.
-  base::Lock lock_;
-  bool rendering_;
-  VideoRendererSink::RenderCallback* callback_;
-
   DISALLOW_COPY_AND_ASSIGN(VideoFrameCompositor);
 };
 
 }  // namespace media
 
 #endif  // MEDIA_BLINK_VIDEO_FRAME_COMPOSITOR_H_