Mojo: More work towards sending message pipe handles over remote message pipes.

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 1956b077d0e7639cffa078786feb38e104f828f8..0036bc1f66863b665a73b423a95d245cbfa4819b 100644
--- a/mojo/system/proxy_message_pipe_endpoint.h
+++ b/mojo/system/proxy_message_pipe_endpoint.h
@@ -21,6 +21,7 @@ namespace mojo {
 namespace system {
 
 class Channel;
+class MessagePipe;
 
 // A |ProxyMessagePipeEndpoint| connects an end of a |MessagePipe| to a
 // |Channel|, over which it transmits and receives data (to/from another
@@ -54,6 +55,14 @@ class MOJO_SYSTEM_IMPL_EXPORT ProxyMessagePipeEndpoint
   virtual void Run(MessageInTransit::EndpointId remote_id) OVERRIDE;
 
  private:
+  struct PreflightDispatcherInfo {
+    PreflightDispatcherInfo() : message_pipe(), port() {}
+
+    // For now, we only support sending message pipes, so this is simple.
+    MessagePipe* message_pipe;
+    unsigned port;
+  };
+
   bool is_attached() const {
     return !!channel_.get();
   }
@@ -62,9 +71,15 @@ class MOJO_SYSTEM_IMPL_EXPORT ProxyMessagePipeEndpoint
     return remote_id_ != MessageInTransit::kInvalidEndpointId;
   }
 
-  MojoResult CanEnqueueDispatchers(const std::vector<Dispatcher*>* dispatchers);
+  // Checks that |dispatchers| will be able to be enqueued by
+  // |EnqueueMessageInternal()| (which then MUST be called if this succeeds).
+  // |dispatchers| must be non-null and nonempty; |preflight_dispatcher_infos|
+  // must be non-null and empty.
+  MojoResult PreflightDispatchers(
+      const std::vector<Dispatcher*>* dispatchers,
+      std::vector<PreflightDispatcherInfo>* preflight_dispatcher_infos);
   // |dispatchers| should be non-null only if it's nonempty, in which case the
-  // dispatchers should have been preflighted by |CanEnqueueDispatchers()|.
+  // dispatchers should have been preflighted by |PreflightDispatchers()|.
   void EnqueueMessageInternal(MessageInTransit* message,
                               const std::vector<Dispatcher*>* dispatchers);