Move IPC::MessageFilter and router to a separate file

content/public/test/mock_render_thread.cc

Index: content/public/test/mock_render_thread.cc
diff --git a/content/public/test/mock_render_thread.cc b/content/public/test/mock_render_thread.cc
index ba66d333b6dc2de5ae9b2130992cab27e4e5dcd0..652842acf5d55c84bfc980c4fedb2c4e7c24fcb8 100644
--- a/content/public/test/mock_render_thread.cc
+++ b/content/public/test/mock_render_thread.cc
@@ -9,6 +9,7 @@
 #include "content/common/view_messages.h"
 #include "content/public/renderer/render_process_observer.h"
 #include "content/renderer/render_view_impl.h"
+#include "ipc/ipc_message_filter.h"
 #include "ipc/ipc_message_utils.h"
 #include "ipc/ipc_sync_message.h"
 #include "testing/gtest/include/gtest/gtest.h"
@@ -27,7 +28,7 @@ MockRenderThread::MockRenderThread()
 
 MockRenderThread::~MockRenderThread() {
   while (!filters_.empty()) {
-    scoped_refptr<IPC::ChannelProxy::MessageFilter> filter = filters_.back();
+    scoped_refptr<IPC::MessageFilter> filter = filters_.back();
     filters_.pop_back();
     filter->OnFilterRemoved();
   }
@@ -93,14 +94,14 @@ int MockRenderThread::GenerateRoutingID() {
   return MSG_ROUTING_NONE;
 }
 
-void MockRenderThread::AddFilter(IPC::ChannelProxy::MessageFilter* filter) {
+void MockRenderThread::AddFilter(IPC::MessageFilter* filter) {
   filter->OnFilterAdded(&sink());
   // Add this filter to a vector so the MockRenderThread::RemoveFilter function
   // can check if this filter is added.
   filters_.push_back(make_scoped_refptr(filter));
 }
 
-void MockRenderThread::RemoveFilter(IPC::ChannelProxy::MessageFilter* filter) {
+void MockRenderThread::RemoveFilter(IPC::MessageFilter* filter) {
   // Emulate the IPC::ChannelProxy::OnRemoveFilter function.
   for (size_t i = 0; i < filters_.size(); ++i) {
     if (filters_[i].get() == filter) {