Implements AudioMessageFilter as member in RenderThread

content/renderer/media/audio_message_filter.h

Index: content/renderer/media/audio_message_filter.h
===================================================================
--- content/renderer/media/audio_message_filter.h	(revision 89207)
+++ content/renderer/media/audio_message_filter.h	(working copy)
@@ -13,6 +13,7 @@
 
 #include "base/gtest_prod_util.h"
 #include "base/id_map.h"
+#include "base/memory/singleton.h"
 #include "base/shared_memory.h"
 #include "base/sync_socket.h"
 #include "content/common/audio_stream_state.h"
@@ -52,9 +53,11 @@
     virtual ~Delegate() {}
   };
 
-  explicit AudioMessageFilter(int32 route_id);
-  virtual ~AudioMessageFilter();
+  static AudioMessageFilter* GetInstance();
 
+  // Sets the routing ID for all transmitted messages.
+  void SetRoutingID(int32 id);
+
   // Add a delegate to the map and return id of the entry.
   int32 AddDelegate(Delegate* delegate);
 
@@ -66,9 +69,12 @@
 
   MessageLoop* message_loop() { return message_loop_; }
 
+  int32 routing_id() { return routing_id_; }
+
  private:
-  // For access to |message_loop_|.
-  friend class AudioRendererImplTest;
+  friend struct DefaultSingletonTraits<AudioMessageFilter>;
+  AudioMessageFilter();
+  virtual ~AudioMessageFilter();
 
   FRIEND_TEST_ALL_PREFIXES(AudioMessageFilterTest, Basic);
   FRIEND_TEST_ALL_PREFIXES(AudioMessageFilterTest, Delegates);
@@ -110,7 +116,7 @@
 
   IPC::Channel* channel_;
 
-  int32 route_id_;
+  int32 routing_id_;
 
   MessageLoop* message_loop_;