Use FF_THREAD_SLICE threading mode in FFmpeg for MediaSource streams.

media/filters/ffmpeg_video_decoder.h

Index: media/filters/ffmpeg_video_decoder.h
diff --git a/media/filters/ffmpeg_video_decoder.h b/media/filters/ffmpeg_video_decoder.h
index 07cf2be2475eca53e6b2add3fdbaa8b4574a1731..014c206d173517fccb48c35c514e7549c5549ab1 100644
--- a/media/filters/ffmpeg_video_decoder.h
+++ b/media/filters/ffmpeg_video_decoder.h
@@ -29,8 +29,21 @@ class ScopedPtrAVFreeFrame;
 
 class MEDIA_EXPORT FFmpegVideoDecoder : public VideoDecoder {
  public:
-  explicit FFmpegVideoDecoder(
-      const scoped_refptr<base::SingleThreadTaskRunner>& task_runner);
+  // Threading mode determines how frames should be distributed between
+  // decoding threads.
+  enum ThreadingMode {
+    // Each thread decode a single frame and multiple frames may be decoded in

[Ami GONE FROM CHROMIUM, 2014/01/28 07:17:10]

s/decode/decodes/

+    // parallel. In this mode FFmpeg will delay N-1 frames when using N threads.
+    THREADING_FRAME,
+
+    // Each frame is distributed between decode threads. If the video contains
+    // only one slice per frame then only one thread will be used for decoding.
+    THREADING_SLICE,
+  };
+
+  FFmpegVideoDecoder(
+      const scoped_refptr<base::SingleThreadTaskRunner>& task_runner,
+      ThreadingMode threading_mode);
   virtual ~FFmpegVideoDecoder();
 
   // VideoDecoder implementation.
@@ -72,6 +85,8 @@ class MEDIA_EXPORT FFmpegVideoDecoder : public VideoDecoder {
   void DoReset();
 
   scoped_refptr<base::SingleThreadTaskRunner> task_runner_;
+  ThreadingMode threading_mode_;
+
   base::WeakPtrFactory<FFmpegVideoDecoder> weak_factory_;
   base::WeakPtr<FFmpegVideoDecoder> weak_this_;