Added API Dart_PostCMessage for posting a Dart_CMessage structure

runtime/vm/dart_api_impl.cc

Index: runtime/vm/dart_api_impl.cc
diff --git a/runtime/vm/dart_api_impl.cc b/runtime/vm/dart_api_impl.cc
index b23cdb0242af685df616292a2cbd90d08f7a1bc9..bc8d3ea384dcd685ea2d8e2d841b37efc1455abc 100644
--- a/runtime/vm/dart_api_impl.cc
+++ b/runtime/vm/dart_api_impl.cc
@@ -730,6 +730,19 @@ DART_EXPORT bool Dart_PostIntArray(Dart_Port port_id,
 }
 
 
+DART_EXPORT bool Dart_PostCMessage(Dart_Port port_id,
+                                   Dart_CMessage* message) {
+  uint8_t* buffer = NULL;
+  MessageWriter writer(&buffer, allocator);
+
+  writer.WriteCMessage(message->root);
+
+  // Post the message at the given port.
+  return PortMap::PostMessage(new Message(
+      port_id, Message::kIllegalPort, buffer, Message::kNormalPriority));
+}
+
+
 DART_EXPORT bool Dart_Post(Dart_Port port_id, Dart_Handle handle) {
   Isolate* isolate = Isolate::Current();
   CHECK_ISOLATE(isolate);