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 89645)
+++ 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/media/audio_stream_state.h"
@@ -52,9 +53,20 @@
     virtual ~Delegate() {}
   };
 
-  explicit AudioMessageFilter(int32 route_id);
-  virtual ~AudioMessageFilter();
+  enum RoutingIDs {
+    // Indicates that we don't have a routing ID yet.
+    ROUTING_ID_HAS_NOT_BEEN_SET = -1,

[scherkus (not reviewing), 2011/06/21 17:24:00]

this doesn't need to be in .h file

also kCamelCaseStyle

so you could move this to .cc and have kNoRoutingId = -1

[jam, 2011/06/21 19:02:04]

we already have a value for this: MSG_ROUTING_NONE

+  };
 
+  // Classes using the Singleton<T> pattern should declare a GetInstance()
+  // method and call Singleton::get() from within that.
+  static AudioMessageFilter* GetInstance();
+
+  // Sets the routing ID for all transmitted messages.
+  void SetRoutingID(int32 id);

[scherkus (not reviewing), 2011/06/21 17:24:00]

I'm not too hot on having every callee remember to call these two methods in
order to use AudioMessageFilter...

how about changing GetInstance to accept a routing_id

that way the check-and-set of the routing_id can be contained inside
GetInstance() and we're guaranteed that when returning the AudioMessageFilter
it's ready to use immediately

+
+  bool RoutingIDHasBeenSet() const;
+
   // Add a delegate to the map and return id of the entry.
   int32 AddDelegate(Delegate* delegate);
 
@@ -66,10 +78,16 @@
 
   MessageLoop* message_loop() { return message_loop_; }
 
+  int32 routing_id() { return routing_id_; }

[scherkus (not reviewing), 2011/06/21 17:24:00]

I don't think I saw anyone actually call this method.. we might be able to
remove it

+
  private:
-  // For access to |message_loop_|.
-  friend class AudioRendererImplTest;
+  // This allows constructor and destructor to be private and usable only
+  // by the Singleton class.
+  friend struct RefCountedSingletonTraits<AudioMessageFilter>;
 
+  AudioMessageFilter();
+  virtual ~AudioMessageFilter();
+
   FRIEND_TEST_ALL_PREFIXES(AudioMessageFilterTest, Basic);
   FRIEND_TEST_ALL_PREFIXES(AudioMessageFilterTest, Delegates);
 
@@ -110,7 +128,7 @@
 
   IPC::Channel* channel_;
 
-  int32 route_id_;
+  int32 routing_id_;
 
   MessageLoop* message_loop_;