Move IPC::MessageFilter and router to a separate file

content/plugin/plugin_thread.cc

Index: content/plugin/plugin_thread.cc
diff --git a/content/plugin/plugin_thread.cc b/content/plugin/plugin_thread.cc
index 9c7519afbb6ce2dd0861c31af1ba59dd9ed84935..bec0f98d887ecf5af762ab6676bed77a61d5a2c4 100644
--- a/content/plugin/plugin_thread.cc
+++ b/content/plugin/plugin_thread.cc
@@ -28,19 +28,20 @@
 #include "content/public/plugin/content_plugin_client.h"
 #include "third_party/WebKit/public/web/WebKit.h"
 #include "ipc/ipc_channel_handle.h"
+#include "ipc/message_filter.h"
 
 namespace content {
 
 namespace {
 
-class EnsureTerminateMessageFilter : public IPC::ChannelProxy::MessageFilter {
+class EnsureTerminateMessageFilter : public IPC::MessageFilter {
  public:
   EnsureTerminateMessageFilter() {}
 
  protected:
   virtual ~EnsureTerminateMessageFilter() {}
 
-  // IPC::ChannelProxy::MessageFilter:
+  // IPC::MessageFilter:
   virtual void OnChannelError() OVERRIDE {
     // How long we wait before forcibly shutting down the process.
     const base::TimeDelta kPluginProcessTerminateTimeout =