Move passing of WebRTC rendering frames to IO thread

content/renderer/media/webmediaplayer_ms_compositor.h

 // Copyright 2015 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_WEBMEDIAPLAYER_MS_COMPOSITOR_H_
 #define CONTENT_RENDERER_MEDIA_WEBMEDIAPLAYER_MS_COMPOSITOR_H_
 
 #include <stddef.h>
 
 #include <map>
@@ skipping 21 matching lines @@
 
 namespace media {
 class VideoRendererAlgorithm;
 }
 
 namespace content {
 class WebMediaPlayerMS;
 
 // This class is designed to handle the work load on compositor thread for
 // WebMediaPlayerMS. It will be instantiated on the main thread, but destroyed
-// on the compositor thread.
+// on the thread holding the last reference.
 //
 // WebMediaPlayerMSCompositor utilizes VideoRendererAlgorithm to store the
 // incoming frames and select the best frame for rendering to maximize the
 // smoothness, if REFERENCE_TIMEs are populated for incoming VideoFrames.
 // Otherwise, WebMediaPlayerMSCompositor will simply store the most recent
 // frame, and submit it whenever asked by the compositor.
 class CONTENT_EXPORT WebMediaPlayerMSCompositor
-    : public NON_EXPORTED_BASE(cc::VideoFrameProvider) {
+    : public NON_EXPORTED_BASE(cc::VideoFrameProvider),
+      public base::RefCountedThreadSafe<WebMediaPlayerMSCompositor> {
  public:
   // This |url| represents the media stream we are rendering. |url| is used to
   // find out what web stream this WebMediaPlayerMSCompositor is playing, and
   // together with flag "--disable-rtc-smoothness-algorithm" determine whether
   // we enable algorithm or not.
   WebMediaPlayerMSCompositor(
       const scoped_refptr<base::SingleThreadTaskRunner>& compositor_task_runner,
       const blink::WebMediaStream& web_stream,
       const base::WeakPtr<WebMediaPlayerMS>& player);
 
-  ~WebMediaPlayerMSCompositor() override;
-
   void EnqueueFrame(scoped_refptr<media::VideoFrame> frame);
 
   // Statistical data
   gfx::Size GetCurrentSize();
   base::TimeDelta GetCurrentTime();
   size_t total_frame_count() const;
   size_t dropped_frame_count() const;
 
   // VideoFrameProvider implementation.
   void SetVideoFrameProviderClient(
       cc::VideoFrameProvider::Client* client) override;
   bool UpdateCurrentFrame(base::TimeTicks deadline_min,
                           base::TimeTicks deadline_max) override;
   bool HasCurrentFrame() override;
   scoped_refptr<media::VideoFrame> GetCurrentFrame() override;
   void PutCurrentFrame() override;
 
   // Return the current frame being rendered.
   // Difference between GetCurrentFrame(): GetCurrentFrame() is designed for
   // chrome compositor to pull frame from WebMediaPlayerMSCompositor, and thus
   // calling GetCurrentFrame() will affect statistics like |dropped_frames_|
   // etc. Calling this function has no side effect.
   scoped_refptr<media::VideoFrame> GetCurrentFrameWithoutUpdatingStatistics();
 
   void StartRendering();
   void StopRendering();
   void ReplaceCurrentFrameWithACopy();
 
+  // Tell |video_frame_provider_client_| to stop using this instance in
+  // preparation for dtor.
+  void StopUsingProvider();
+
  private:
+  friend class base::RefCountedThreadSafe<WebMediaPlayerMSCompositor>;
   friend class WebMediaPlayerMSTest;
 
+  ~WebMediaPlayerMSCompositor() override;
+
   bool MapTimestampsToRenderTimeTicks(
       const std::vector<base::TimeDelta>& timestamps,
       std::vector<base::TimeTicks>* wall_clock_times);
 
-  void SetCurrentFrame(const scoped_refptr<media::VideoFrame>& frame);
-
   // For algorithm enabled case only: given the render interval, update
   // current_frame_ and dropped_frame_count_.
   void Render(base::TimeTicks deadline_min, base::TimeTicks deadline_max);
 
+  void SetCurrentFrame(const scoped_refptr<media::VideoFrame>& frame);

[qiangchen, 2016/12/05 18:54:57]

Can you order this before Render function to kill this extra diff.

[emircan, 2016/12/06 00:36:43]

I wanted to sync the order of declaration/definition in these files while I am
already adding new functions.

+
   void StartRenderingInternal();
   void StopRenderingInternal();
+  void StopUsingProviderInternal();
 
   void SetAlgorithmEnabledForTesting(bool algorithm_enabled);
 
   // Used for DCHECKs to ensure method calls executed in the correct thread.
   base::ThreadChecker thread_checker_;
+  base::ThreadChecker media_thread_checker_;
 
   scoped_refptr<base::SingleThreadTaskRunner> compositor_task_runner_;
   base::MessageLoop* main_message_loop_;
 
   base::WeakPtr<WebMediaPlayerMS> player_;
 
   size_t serial_;
 
   // A pointer back to the compositor to inform it about state changes. This
   // is not |nullptr| while the compositor is actively using this
@@ skipping 20 matching lines @@
   // Historical data about last rendering. These are for detecting whether
   // rendering is paused (one reason is that the tab is not in the front), in
   // which case we need to do background rendering.
   base::TimeTicks last_deadline_max_;
   base::TimeDelta last_render_length_;
 
   size_t total_frame_count_;
   size_t dropped_frame_count_;
 
   bool stopped_;
+  bool provider_in_use_;

[qiangchen, 2016/12/05 18:54:57]

Can you simply set video_frame_provider_client_ to nullptr in the implementation
of StopUsingProvider. And thus |provider_in_use_|==true is equivalent as
|video_frame_provier_client_|!=nullptr, and thus we can avoid |provider_in_use_|
variable.

[emircan, 2016/12/06 00:36:43]

Done.

 
   std::map<base::TimeDelta, base::TimeTicks> timestamps_to_clock_times_;
 
   // |current_frame_lock_| protects |current_frame_used_by_compositor_|,
   // |current_frame_|, and |rendering_frame_buffer_|.
   base::Lock current_frame_lock_;
 
-  // Make sure the weak pointer factory member is the last member of the class.
-  base::WeakPtrFactory<WebMediaPlayerMSCompositor> weak_ptr_factory_;
-
   DISALLOW_COPY_AND_ASSIGN(WebMediaPlayerMSCompositor);
 };
 }  // namespace content
 
 #endif  // CONTENT_RENDERER_MEDIA_WEBMEDIAPLAYER_MS_COMPOSITOR_H_