Change MediaFilter::Stop() to accept a callback so that Stop() is asynchronous.

media/base/mock_filters.cc

-// Copyright (c) 2009 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.
+// Copyright (c) 2010 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.
 
 #include "media/base/mock_filters.h"
 
 namespace media {
 
 void RunFilterCallback(::testing::Unused, FilterCallback* callback) {
   callback->Run();
   delete callback;
 }
 
 void DestroyFilterCallback(::testing::Unused, FilterCallback* callback) {
   delete callback;
 }
 
+void RunStopFilterCallback(FilterCallback* callback) {
+  callback->Run();
+  delete callback;
+}
+
 }  // namespace media