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

runtime/vm/isolate.cc

Index: runtime/vm/isolate.cc
diff --git a/runtime/vm/isolate.cc b/runtime/vm/isolate.cc
index f8133efa01441bf6c2a1b3e9a705498c4d8cb102..4617be183a556b63309baf6c8d8ddb0e4561c0e5 100644
--- a/runtime/vm/isolate.cc
+++ b/runtime/vm/isolate.cc
@@ -468,24 +468,29 @@ MessageHandler::MessageStatus IsolateMessageHandler::HandleMessage(
   }
 
   // Parse the message.
-  MessageSnapshotReader reader(message->data(), message->len(), thread);
-  const Object& msg_obj = Object::Handle(zone, reader.ReadObject());
-  if (msg_obj.IsError()) {
-    // An error occurred while reading the message.
-    delete message;
-    return ProcessUnhandledException(Error::Cast(msg_obj));
-  }
-  if (!msg_obj.IsNull() && !msg_obj.IsInstance()) {
-    // TODO(turnidge): We need to decide what an isolate does with
-    // malformed messages.  If they (eventually) come from a remote
-    // machine, then it might make sense to drop the message entirely.
-    // In the case that the message originated locally, which is
-    // always true for now, then this should never occur.
-    UNREACHABLE();
-  }
-
   Instance& msg = Instance::Handle(zone);
-  msg ^= msg_obj.raw();  // Can't use Instance::Cast because may be null.
+  if (message->len() > 0) {

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

How about turning it around:
if (message->IsRaw()) {
  msg_obj = message->raw_obj();
  ASSERT(msg_obj.IsSmi() || msg_obj.InVMHeap());
} else {
  // Deserialize the message object.
  ...
}

// Error checking should be done in both cases too.

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

Done.

+    MessageSnapshotReader reader(message->data(), message->len(), thread);
+    const Object& msg_obj = Object::Handle(zone, reader.ReadObject());
+    if (msg_obj.IsError()) {
+      // An error occurred while reading the message.
+      delete message;
+      return ProcessUnhandledException(Error::Cast(msg_obj));
+    }
+    if (!msg_obj.IsNull() && !msg_obj.IsInstance()) {
+      // TODO(turnidge): We need to decide what an isolate does with
+      // malformed messages.  If they (eventually) come from a remote
+      // machine, then it might make sense to drop the message entirely.
+      // In the case that the message originated locally, which is
+      // always true for now, then this should never occur.
+      UNREACHABLE();
+    }
+    msg ^= msg_obj.raw();  // Can't use Instance::Cast because may be null.
+  } else {
+    ASSERT(message->len() == 0);
+    msg ^= message->raw_obj();
+    ASSERT(msg.IsSmi() || msg.InVMHeap());
+  }
 
   MessageStatus status = kOK;
   if (message->IsOOB()) {