Adds a special case for sending an int over a port with the native API.

runtime/vm/native_message_handler.cc

Index: runtime/vm/native_message_handler.cc
diff --git a/runtime/vm/native_message_handler.cc b/runtime/vm/native_message_handler.cc
index 8f8d7a6971c725426060d8f1a5aa9aa6d4666a95..0e4002c5eebc80b86132dd0dcf554c0c6da88ad6 100644
--- a/runtime/vm/native_message_handler.cc
+++ b/runtime/vm/native_message_handler.cc
@@ -38,6 +38,7 @@ MessageHandler::MessageStatus NativeMessageHandler::HandleMessage(
     // We currently do not use OOB messages for native ports.
     UNREACHABLE();
   }
+  ASSERT(message->len() > 0);

[Ivan Posva, 2015/12/09 22:45:28]

You cannot assert this. The poster of the message on the other side is free to
use the shortcut without knowing who the recipient is.

[zra, 2015/12/10 00:07:29]

I'm not sure I see a good way to convert a RawObject to a Dart_CObject, here. I
could try to serialize the RawObject as if it had been posted by Dart_Post, but
the problem there is that the NativeMessageHandlers run on a thread that doesn't
have an Isolate or Thread, which the SnapshotWriter assumes exists.

Thoughts?

[zra, 2015/12/10 20:51:33]

I've added some code to this CL to handle RawObject -> CObject conversion of
Smis and Null. I put it in //runtime/vm/dart_api_message.h. PTAL.

   // We create a native scope for handling the message.
   // All allocation of objects for decoding the message is done in the
   // zone associated with this scope.