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

media/base/pipeline.h

 // 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.
 
 // The pipeline is the public API clients use for playing back media.  Clients
 // provide a filter factory containing the filters they want the pipeline to
 // use to render media.
 
 #ifndef MEDIA_BASE_PIPELINE_H_
 #define MEDIA_BASE_PIPELINE_H_
 
 #include <string>
 
 #include "base/callback.h"
 #include "media/base/factory.h"
 
 namespace base {
 class TimeDelta;
 }
 
 namespace media {
 
 // Error definitions for pipeline.  All codes indicate an error except:
 // PIPELINE_OK indicates the pipeline is running normally.
-// PIPELINE_STOPPING is used internally when Pipeline::Stop() is called.
 enum PipelineError {
   PIPELINE_OK,
-  PIPELINE_STOPPING,
   PIPELINE_ERROR_URL_NOT_FOUND,
   PIPELINE_ERROR_NETWORK,
   PIPELINE_ERROR_DECODE,
   PIPELINE_ERROR_ABORT,
   PIPELINE_ERROR_INITIALIZATION_FAILED,
   PIPELINE_ERROR_REQUIRED_FILTER_MISSING,
   PIPELINE_ERROR_OUT_OF_MEMORY,
   PIPELINE_ERROR_COULD_NOT_RENDER,
   PIPELINE_ERROR_READ,
   PIPELINE_ERROR_AUDIO_HARDWARE,
@@ skipping 122 matching lines @@
 
  protected:
   // Only allow ourselves to be deleted by reference counting.
   friend class base::RefCountedThreadSafe<Pipeline>;
   virtual ~Pipeline() {}
 };
 
 }  // namespace media
 
 #endif  // MEDIA_BASE_PIPELINE_H_