Move IPC::MessageFilter and router to a separate file

content/common/gpu/gpu_channel.h

Index: content/common/gpu/gpu_channel.h
diff --git a/content/common/gpu/gpu_channel.h b/content/common/gpu/gpu_channel.h
index b51f845e3744cdb7063105e6d65359b3d179ed7b..390313519b025804a433583f650191275be37418 100644
--- a/content/common/gpu/gpu_channel.h
+++ b/content/common/gpu/gpu_channel.h
@@ -38,6 +38,10 @@ class ImageManager;
 }
 }
 
+namespace IPC {
+class MessageFilter;
+}
+
 namespace content {
 class DevToolsGpuAgent;
 class GpuChannelManager;
@@ -145,8 +149,8 @@ class GpuChannel : public IPC::Listener,
 
   void CacheShader(const std::string& key, const std::string& shader);
 
-  void AddFilter(IPC::ChannelProxy::MessageFilter* filter);
-  void RemoveFilter(IPC::ChannelProxy::MessageFilter* filter);
+  void AddFilter(IPC::MessageFilter* filter);
+  void RemoveFilter(IPC::MessageFilter* filter);
 
   uint64 GetMemoryUsage();