Move IPC::MessageFilter and router to a separate file

content/browser/renderer_host/render_message_filter.h

Index: content/browser/renderer_host/render_message_filter.h
diff --git a/content/browser/renderer_host/render_message_filter.h b/content/browser/renderer_host/render_message_filter.h
index a82ed94dc163fb36bb4554f07940494aa236b2a5..3c42f53d453ec12bc173a9695bfddf04878e45bc 100644
--- a/content/browser/renderer_host/render_message_filter.h
+++ b/content/browser/renderer_host/render_message_filter.h
@@ -23,6 +23,7 @@
 #include "content/common/pepper_renderer_instance_data.h"
 #include "content/public/browser/browser_message_filter.h"
 #include "content/public/common/three_d_api_types.h"
+#include "ipc/message_filter.h"
 #include "media/audio/audio_parameters.h"
 #include "media/base/channel_layout.h"
 #include "net/cookies/canonical_cookie.h"
@@ -95,7 +96,7 @@ class RenderMessageFilter : public BrowserMessageFilter {
                       MediaInternals* media_internals,
                       DOMStorageContextWrapper* dom_storage_context);
 
-  // IPC::ChannelProxy::MessageFilter methods:
+  // IPC::MessageFilter methods:
   virtual void OnChannelClosing() OVERRIDE;
   virtual void OnChannelConnected(int32 peer_pid) OVERRIDE;