Mojo: Use new message APIs to reduce copying

mojo/public/cpp/bindings/lib/router.cc

Index: mojo/public/cpp/bindings/lib/router.cc
diff --git a/mojo/public/cpp/bindings/lib/router.cc b/mojo/public/cpp/bindings/lib/router.cc
index 66d7e36def9f923587b5f5c633aa6c97c5de52c3..da5f34b1df57ce4bbfaf8668061d2bbde6bc3e49 100644
--- a/mojo/public/cpp/bindings/lib/router.cc
+++ b/mojo/public/cpp/bindings/lib/router.cc
@@ -153,11 +153,12 @@ bool Router::AcceptWithResponder(Message* message, MessageReceiver* responder) {
   if (request_id == 0)
     request_id = next_request_id_++;
 
+  bool is_sync = message->has_flag(kMessageIsSync);
   message->set_request_id(request_id);
   if (!connector_.Accept(message))
     return false;
 
-  if (!message->has_flag(kMessageIsSync)) {
+  if (!is_sync) {
     // We assume ownership of |responder|.
     async_responders_[request_id] = base::WrapUnique(responder);
     return true;