Pass in media message loop to VideoRendererBase and enforce calling on the right thread.

media/filters/video_renderer_base.h

Index: media/filters/video_renderer_base.h
diff --git a/media/filters/video_renderer_base.h b/media/filters/video_renderer_base.h
index 85e6527c68112d60f56de6b729b5fa13e047f5ed..7ff82da5e1b7c045d3343314008f2a2f7430f9b3 100644
--- a/media/filters/video_renderer_base.h
+++ b/media/filters/video_renderer_base.h
@@ -17,6 +17,10 @@
 #include "media/base/video_frame.h"
 #include "media/base/video_renderer.h"
 
+namespace base {
+class MessageLoopProxy;
+}
+
 namespace media {
 
 // VideoRendererBase creates its own thread for the sole purpose of timing frame
@@ -48,7 +52,8 @@ class MEDIA_EXPORT VideoRendererBase
   // Get/PutCurrentFrame() http://crbug.com/108435
   VideoRendererBase(const base::Closure& paint_cb,
                     const SetOpaqueCB& set_opaque_cb,
-                    bool drop_frames);
+                    bool drop_frames,
+                    const scoped_refptr<base::MessageLoopProxy>& message_loop);

[Ami GONE FROM CHROMIUM, 2012/11/29 23:34:23]

could alternatively let the decoder tell the renderer what loop it lives on.

[scherkus (not reviewing), 2012/11/29 23:45:56]

I'm mulling over this one

the "caller has to know the right msg loop" model requires that the caller is
given a handle at some point. either it's provided up front (this PS) or as you
suggest the decoder can expose it

my gut tells me the latter is less optimal for some reason -- perhaps because we
have everything running on the same thread today so it seems unnecessary in the
long run i.e., VRB should be fixed to run on message_loop_

 
   // VideoRenderer implementation.
   virtual void Initialize(const scoped_refptr<DemuxerStream>& stream,
@@ -249,6 +254,8 @@ class MEDIA_EXPORT VideoRendererBase
   // The last natural size |size_changed_cb_| was called with.
   gfx::Size last_natural_size_;
 
+  scoped_refptr<base::MessageLoopProxy> decoder_message_loop_;
+
   DISALLOW_COPY_AND_ASSIGN(VideoRendererBase);
 };