Move IPC::MessageFilter and router to a separate file

content/common/child_process_host_impl.h

Index: content/common/child_process_host_impl.h
diff --git a/content/common/child_process_host_impl.h b/content/common/child_process_host_impl.h
index 57a410b51053d67c04522a9f779ccc79425aa110..1daa5d540763bab9d08b8fe91e2e6052f2162b7f 100644
--- a/content/common/child_process_host_impl.h
+++ b/content/common/child_process_host_impl.h
@@ -26,6 +26,10 @@ namespace gfx {
 struct GpuMemoryBufferHandle;
 }
 
+namespace IPC {
+class MessageFilter;
+}
+
 namespace content {
 class ChildProcessHostDelegate;
 
@@ -58,7 +62,7 @@ class CONTENT_EXPORT ChildProcessHostImpl : public ChildProcessHost,
   virtual void ForceShutdown() OVERRIDE;
   virtual std::string CreateChannel() OVERRIDE;
   virtual bool IsChannelOpening() OVERRIDE;
-  virtual void AddFilter(IPC::ChannelProxy::MessageFilter* filter) OVERRIDE;
+  virtual void AddFilter(IPC::MessageFilter* filter) OVERRIDE;
 #if defined(OS_POSIX)
   virtual int TakeClientFileDescriptor() OVERRIDE;
 #endif
@@ -91,7 +95,7 @@ class CONTENT_EXPORT ChildProcessHostImpl : public ChildProcessHost,
   // Holds all the IPC message filters.  Since this object lives on the IO
   // thread, we don't have a IPC::ChannelProxy and so we manage filters
   // manually.
-  std::vector<scoped_refptr<IPC::ChannelProxy::MessageFilter> > filters_;
+  std::vector<scoped_refptr<IPC::MessageFilter> > filters_;
 
   DISALLOW_COPY_AND_ASSIGN(ChildProcessHostImpl);
 };