Replace MessageLoopProxy with SingleThreadTaskRunner for media/filters/ + associated code.

media/filters/gpu_video_accelerator_factories.h

Index: media/filters/gpu_video_accelerator_factories.h
diff --git a/media/filters/gpu_video_accelerator_factories.h b/media/filters/gpu_video_accelerator_factories.h
index c152c2a4bda8ca51d0769ac047a85bb27e4ce2b3..b6de58f4a239d2b22eee8a21b5435f9c4754cf7c 100644
--- a/media/filters/gpu_video_accelerator_factories.h
+++ b/media/filters/gpu_video_accelerator_factories.h
@@ -11,7 +11,7 @@
 #include "media/video/video_encode_accelerator.h"
 
 namespace base {
-class MessageLoopProxy;
+class SingleThreadTaskRunner;
 class SharedMemory;
 }
 
@@ -52,8 +52,8 @@ class MEDIA_EXPORT GpuVideoAcceleratorFactories
   // Close()ing the returned pointer.
   virtual base::SharedMemory* CreateSharedMemory(size_t size) = 0;
 
-  // Returns the message loop the video accelerator runs on.
-  virtual scoped_refptr<base::MessageLoopProxy> GetMessageLoop() = 0;
+  // Returns the task runner the video accelerator runs on.
+  virtual scoped_refptr<base::SingleThreadTaskRunner> GetTaskRunner() = 0;

[Ami GONE FROM CHROMIUM, 2013/11/08 16:54:46]

This change (here and elsewhere) is not a semantic no-op.  
Before, a reader of the callsite of GetMessageLoop() knew that the returned
thing was very likely mapped 1:1 with a thread.  The same can't be said for
GetTaskRunner(), since TaskRunner could be backed by multiple threads.  
GetSingleThreadTaskRunner is too long to be a palatable fix for this
shortcoming, though.

I don't have a good suggestion, just wanted to call this out.  Maybe you have
ideas.
Doesn't need to block the CL.

[scherkus (not reviewing), 2013/11/08 21:51:39]

I'm OK leaving the name as is since the return type encodes the type of
TaskRunner it is. It's not perfect ... but I also don't feel it's worth
re-encoding that information in the method name.

FWIW (and I know this isn't a compelling argument!), Get{Foo}TaskRunner() seems
to be the pattern that's emerged in Chromium and they all return a variety of
TaskRunners: http://goo.gl/NksxFF

 
   // Abort any outstanding factory operations and error any future
   // attempts at factory operations