Move IPC::MessageFilter and router to a separate file

content/browser/gpu/gpu_process_host.cc

Index: content/browser/gpu/gpu_process_host.cc
diff --git a/content/browser/gpu/gpu_process_host.cc b/content/browser/gpu/gpu_process_host.cc
index 423107de9e548279d0821e9a6ec2cc852b23bff7..301d03449d147d8187362f0ed7e754d02c541e9b 100644
--- a/content/browser/gpu/gpu_process_host.cc
+++ b/content/browser/gpu/gpu_process_host.cc
@@ -36,6 +36,7 @@
 #include "content/public/common/sandboxed_process_launcher_delegate.h"
 #include "gpu/command_buffer/service/gpu_switches.h"
 #include "ipc/ipc_channel_handle.h"
+#include "ipc/ipc_message_filter.h"
 #include "ipc/ipc_switches.h"
 #include "ui/events/latency_info.h"
 #include "ui/gl/gl_switches.h"
@@ -547,7 +548,7 @@ bool GpuProcessHost::Send(IPC::Message* msg) {
   return result;
 }
 
-void GpuProcessHost::AddFilter(IPC::ChannelProxy::MessageFilter* filter) {
+void GpuProcessHost::AddFilter(IPC::MessageFilter* filter) {
   DCHECK(CalledOnValidThread());
   process_->GetHost()->AddFilter(filter);
 }