media::BindToLoop() is born, with example uses to slim down WebMediaPlayerProxy.

webkit/media/webmediaplayer_impl.h

 // 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.
 
 // Delegate calls from WebCore::MediaPlayerPrivate to Chrome's video player.
 // It contains Pipeline which is the actual media player pipeline, it glues
 // the media player pipeline, data source, audio renderer and renderer.
 // Pipeline would creates multiple threads and access some public methods
 // of this class, so we need to be extra careful about concurrent access of
 // methods and members.
@@ skipping 323 matching lines @@
   WebKit::WebAudioSourceProvider* audio_source_provider_;
 
   scoped_refptr<media::AudioRendererSink> audio_renderer_sink_;
 
   bool is_local_source_;
   bool supports_save_;
 
   // The decryptor that manages decryption keys and decrypts encrypted frames.
   ProxyDecryptor decryptor_;
 
+  // Should be last to ensure destruction order.
+  base::WeakPtrFactory<WebMediaPlayerImpl> weak_this_;
+
   DISALLOW_COPY_AND_ASSIGN(WebMediaPlayerImpl);
 };
 
 }  // namespace webkit_media
 
 #endif  // WEBKIT_MEDIA_WEBMEDIAPLAYER_IMPL_H_