Run VDA::Decode on GPU IO thread if VDA supports it.

media/video/video_decode_accelerator.h

Index: media/video/video_decode_accelerator.h
diff --git a/media/video/video_decode_accelerator.h b/media/video/video_decode_accelerator.h
index 1aa0954ba962226cbb41d0dccac7ec9ead57aab5..2f6ce9bd4ea173200eec90497d5613b6e0950eae 100644
--- a/media/video/video_decode_accelerator.h
+++ b/media/video/video_decode_accelerator.h
@@ -92,7 +92,7 @@ class MEDIA_EXPORT VideoDecodeAccelerator
 
   // Decodes given bitstream buffer. Once decoder is done with processing
   // |bitstream_buffer| it will call NotifyEndOfBitstreamBuffer() with the
-  // bitstream buffer id.
+  // bitstream buffer id. In GPU process, this runs on IO thread.

[Ami GONE FROM CHROMIUM, 2013/08/22 14:52:03]

This is a strange comment considering processes & threads are not mentioned
otherwise in this file.  I'd just drop it.

   // Parameters:
   //  |bitstream_buffer| is the input bitstream that is sent for decoding.
   virtual void Decode(const BitstreamBuffer& bitstream_buffer) = 0;