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..70078fe94ccd4f88d0540e6087d39505e1084c0d 100644
--- a/ipc/ipc_forwarding_message_filter.h
+++ b/ipc/ipc_forwarding_message_filter.h
@@ -19,30 +19,32 @@ namespace IPC {
 // This class can be used to intercept routed messages and
 // deliver them to a different task runner than they would otherwise
 // be sent. Messages are filtered based on type. To route these messages,
-// add a MessageRouter to the handler.
+// add a Handler to the filter.
 //
-// The user of this class implements ForwardingMessageFilter::Client,
+// The user of this class implements ForwardingMessageFilter::Handler,
 // which will receive the intercepted messages, on the specified target thread.
+// The caller must ensure that each handler in |multi_handlers_| outlives the
+// lifetime of the filter.
+// User can add multiple handlers for specific routing id. When messages are
+// arrived, all handlers in |multi_handlers_| for routing id will be executed.
 class IPC_EXPORT ForwardingMessageFilter : public MessageFilter {
  public:
 
   // The handler is invoked on the thread associated with
-  // |target_task_runner| with messages that were intercepted by this filter.
+  // |target_task_runner_| with messages that were intercepted by this filter.
   typedef base::Callback<void(const Message&)> Handler;
 
   // This filter will intercept |message_ids_to_filter| and post
   // them to the provided |target_task_runner|, where they will be given
-  // to |handler|.
-  //
-  // The caller must ensure that |handler| outlives the lifetime of the filter.
+  // to all handlers in the |multi_handlers_|.
   ForwardingMessageFilter(
       const uint32* message_ids_to_filter,
       size_t num_message_ids_to_filter,
       base::TaskRunner* target_task_runner);
 
-  // Define the message routes to be filtered.
+  // Define the message handler 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;
@@ -52,15 +54,16 @@ class IPC_EXPORT ForwardingMessageFilter : public MessageFilter {
 
   std::set<int> message_ids_to_filter_;
 
-  // The handler_ only gets Run on the thread corresponding to
+  // The handler only gets run on the thread corresponding to
   // target_task_runner_.
   scoped_refptr<base::TaskRunner> target_task_runner_;
 
-  // Protects access to routes_.
+  // Protects access to |multi_handlers_|.
   base::Lock handlers_lock_;
 
-  // Indicates the routing_ids for which messages should be filtered.
-  std::map<int, Handler> handlers_;
+  // Maps the routing_id for which messages should be filtered and handlers
+  // which will be routed.
+  std::multimap<int, Handler> multi_handlers_;
 
   DISALLOW_COPY_AND_ASSIGN(ForwardingMessageFilter);
 };