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

media/base/bind_to_loop.h

 // This file was GENERATED by command:
 //     pump.py bind_to_loop.h.pump
 // DO NOT EDIT BY HAND!!!
 
 
 // Copyright (c) 2012 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 MEDIA_BASE_BIND_TO_LOOP_H_
@@ skipping 143 matching lines @@
 
 }  // namespace internal
 
 template<typename T>
 static base::Callback<T> BindToLoop(
     const scoped_refptr<base::MessageLoopProxy>& loop,
     const base::Callback<T>& cb) {
   return base::Bind(&internal::TrampolineHelper<T>::Run, loop, cb);
 }
 
+template<typename T>
+static base::Callback<T> BindToCurrentLoop(
+    const base::Callback<T>& cb) {
+  return base::Bind(&internal::TrampolineHelper<T>::Run,
+                    base::MessageLoopProxy::current(), cb);
+}
+
 }  // namespace media
 
 #endif  // MEDIA_BASE_BIND_TO_LOOP_H_