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

runtime/lib/isolate.cc

Index: runtime/lib/isolate.cc
diff --git a/runtime/lib/isolate.cc b/runtime/lib/isolate.cc
index dc5279824024337979b7a34babd3307d92ddc72c..db080bd10ada83d565690a7cab2e2f06dc9f3c1d 100644
--- a/runtime/lib/isolate.cc
+++ b/runtime/lib/isolate.cc
@@ -106,18 +106,23 @@ DEFINE_NATIVE_ENTRY(SendPortImpl_sendInternal_, 2) {
   // TODO(iposva): Allow for arbitrary messages to be sent.
   GET_NON_NULL_NATIVE_ARGUMENT(Instance, obj, arguments->NativeArgAt(1));
 
-  uint8_t* data = NULL;
-
   const Dart_Port destination_port_id = port.Id();
   const bool can_send_any_object = isolate->origin_id() == port.origin_id();
 
-  MessageWriter writer(&data, &allocator, can_send_any_object);
-  writer.WriteMessage(obj);
-
-  // TODO(turnidge): Throw an exception when the return value is false?
-  PortMap::PostMessage(new Message(destination_port_id,
-                                   data, writer.BytesWritten(),
-                                   Message::kNormalPriority));
+  if (obj.IsSmi() || obj.InVMHeap()) {
+    PortMap::PostMessage(new Message(destination_port_id,
+                                     reinterpret_cast<uint8_t*>(obj.raw()), 0,
+                                     Message::kNormalPriority));
+  } else {
+    uint8_t* data = NULL;
+    MessageWriter writer(&data, &allocator, can_send_any_object);
+    writer.WriteMessage(obj);
+
+    // TODO(turnidge): Throw an exception when the return value is false?
+    PortMap::PostMessage(new Message(destination_port_id,
+                                     data, writer.BytesWritten(),
+                                     Message::kNormalPriority));
+  }
   return Object::null();
 }