Mojo: Refactor some message pipe stuff.

mojo/system/proxy_message_pipe_endpoint.h

Index: mojo/system/proxy_message_pipe_endpoint.h
diff --git a/mojo/system/proxy_message_pipe_endpoint.h b/mojo/system/proxy_message_pipe_endpoint.h
index 6f9068e268c3f0667c2db9d2ed14f0bad95a62ee..1956b077d0e7639cffa078786feb38e104f828f8 100644
--- a/mojo/system/proxy_message_pipe_endpoint.h
+++ b/mojo/system/proxy_message_pipe_endpoint.h
@@ -46,12 +46,9 @@ class MOJO_SYSTEM_IMPL_EXPORT ProxyMessagePipeEndpoint
   // |MessagePipeEndpoint| implementation:
   virtual void Close() OVERRIDE;
   virtual void OnPeerClose() OVERRIDE;
-  virtual MojoResult CanEnqueueMessage(
-      const MessageInTransit* message,
-      const std::vector<Dispatcher*>* dispatchers) OVERRIDE;
-  virtual void EnqueueMessage(
+  virtual MojoResult EnqueueMessage(
       MessageInTransit* message,
-      std::vector<scoped_refptr<Dispatcher> >* dispatchers) OVERRIDE;
+      const std::vector<Dispatcher*>* dispatchers) OVERRIDE;
   virtual void Attach(scoped_refptr<Channel> channel,
                       MessageInTransit::EndpointId local_id) OVERRIDE;
   virtual void Run(MessageInTransit::EndpointId remote_id) OVERRIDE;
@@ -65,6 +62,12 @@ class MOJO_SYSTEM_IMPL_EXPORT ProxyMessagePipeEndpoint
     return remote_id_ != MessageInTransit::kInvalidEndpointId;
   }
 
+  MojoResult CanEnqueueDispatchers(const std::vector<Dispatcher*>* dispatchers);
+  // |dispatchers| should be non-null only if it's nonempty, in which case the
+  // dispatchers should have been preflighted by |CanEnqueueDispatchers()|.
+  void EnqueueMessageInternal(MessageInTransit* message,
+                              const std::vector<Dispatcher*>* dispatchers);
+
 #ifdef NDEBUG
   void AssertConsistentState() const {}
 #else