cc: Make separate interface for BeginFrame ipc from OutputSurface

ipc/ipc_forwarding_message_filter.h

Index: ipc/ipc_forwarding_message_filter.h
diff --git a/ipc/ipc_forwarding_message_filter.h b/ipc/ipc_forwarding_message_filter.h
index 474fbf4591ab7fda7fdd58a5313bf55dc19310ed..a596c32a4a339603dc9a9d4bde56e92c09fdc2ff 100644
--- a/ipc/ipc_forwarding_message_filter.h
+++ b/ipc/ipc_forwarding_message_filter.h
@@ -42,7 +42,7 @@ class IPC_EXPORT ForwardingMessageFilter : public MessageFilter {
 
   // Define the message routes to be filtered.
   void AddRoute(int routing_id, const Handler& handler);
-  void RemoveRoute(int routing_id);
+  void RemoveRoute(int routing_id, const Handler& handler);
 
   // MessageFilter methods:
   virtual bool OnMessageReceived(const Message& message) override;
@@ -60,7 +60,7 @@ class IPC_EXPORT ForwardingMessageFilter : public MessageFilter {
   base::Lock handlers_lock_;
 
   // Indicates the routing_ids for which messages should be filtered.
-  std::map<int, Handler> handlers_;
+  std::multimap<int, Handler> multi_handlers_;
 
   DISALLOW_COPY_AND_ASSIGN(ForwardingMessageFilter);
 };