Move IPC::MessageFilter and router to a separate file

content/public/renderer/render_thread.h

Index: content/public/renderer/render_thread.h
diff --git a/content/public/renderer/render_thread.h b/content/public/renderer/render_thread.h
index 40bcb77512ad794c4c2daa83e5b9a2e7b91d42fb..a545150f9bb01b1286f4d049a603a49747a926bf 100644
--- a/content/public/renderer/render_thread.h
+++ b/content/public/renderer/render_thread.h
@@ -26,6 +26,7 @@ class WaitableEvent;
 }
 
 namespace IPC {
+class MessageFilter;
 class SyncChannel;
 class SyncMessageFilter;
 }
@@ -61,8 +62,8 @@ class CONTENT_EXPORT RenderThread : public IPC::Sender {
   virtual int GenerateRoutingID() = 0;
 
   // These map to IPC::ChannelProxy methods.
-  virtual void AddFilter(IPC::ChannelProxy::MessageFilter* filter) = 0;
-  virtual void RemoveFilter(IPC::ChannelProxy::MessageFilter* filter) = 0;
+  virtual void AddFilter(IPC::MessageFilter* filter) = 0;
+  virtual void RemoveFilter(IPC::MessageFilter* filter) = 0;
 
   // Add/remove observers for the process.
   virtual void AddObserver(RenderProcessObserver* observer) = 0;