Commits http://codereview.chromium.org/7157001/.

content/renderer/media/audio_renderer_impl.h

Index: content/renderer/media/audio_renderer_impl.h
===================================================================
--- content/renderer/media/audio_renderer_impl.h	(revision 92002)
+++ content/renderer/media/audio_renderer_impl.h	(working copy)
@@ -58,7 +58,7 @@
                           public MessageLoop::DestructionObserver {
  public:
   // Methods called on Render thread ------------------------------------------
-  explicit AudioRendererImpl(AudioMessageFilter* filter);
+  explicit AudioRendererImpl();
   virtual ~AudioRendererImpl();
 
   // Methods called on IO thread ----------------------------------------------
@@ -101,6 +101,7 @@
 
   // For access to constructor and IO thread methods.
   friend class AudioRendererImplTest;
+  friend class DelegateCaller;
   FRIEND_TEST_ALL_PREFIXES(AudioRendererImplTest, Stop);
   FRIEND_TEST_ALL_PREFIXES(AudioRendererImplTest,
                            DestroyedMessageLoop_ConsumeAudioSamples);
@@ -144,11 +145,12 @@
   // Should be called before any class instance is created.
   static void set_latency_type(LatencyType latency_type);
 
+  // Helper method for IPC send calls.
+  void Send(IPC::Message* message);
+
   // Used to calculate audio delay given bytes.
   uint32 bytes_per_second_;
 
-  scoped_refptr<AudioMessageFilter> filter_;
-
   // ID of the stream created in the browser process.
   int32 stream_id_;
 
@@ -156,15 +158,15 @@
   scoped_ptr<base::SharedMemory> shared_memory_;
   uint32 shared_memory_size_;
 
+  // Cached audio message filter (lives on the main render thread).
+  scoped_refptr<AudioMessageFilter> filter_;
+
   // Low latency IPC stuff.
   scoped_ptr<base::SyncSocket> socket_;
 
   // That thread waits for audio input.
   scoped_ptr<base::DelegateSimpleThread> audio_thread_;
 
-  // Message loop for the IO thread.
-  MessageLoop* io_loop_;
-
   // Protects:
   // - |stopped_|
   // - |pending_request_|