Enables clean VM shutdown.

runtime/vm/native_api_impl.cc

Index: runtime/vm/native_api_impl.cc
diff --git a/runtime/vm/native_api_impl.cc b/runtime/vm/native_api_impl.cc
index a6688976e9924ee175f08f01754ad6959514374d..09b2cc6975254740473ba766b2721b49ff6208c1 100644
--- a/runtime/vm/native_api_impl.cc
+++ b/runtime/vm/native_api_impl.cc
@@ -23,7 +23,9 @@ static uint8_t* allocator(uint8_t* ptr, intptr_t old_size, intptr_t new_size) {
 }
 
 
-DART_EXPORT bool Dart_PostCObject(Dart_Port port_id, Dart_CObject* message) {
+static bool PostCObject(Dart_Port port_id,
+                        Dart_CObject* message,
+                        Message::Priority priority) {
   uint8_t* buffer = NULL;
   ApiMessageWriter writer(&buffer, allocator);
   bool success = writer.WriteCMessage(message);
@@ -32,7 +34,17 @@ DART_EXPORT bool Dart_PostCObject(Dart_Port port_id, Dart_CObject* message) {
 
   // Post the message at the given port.
   return PortMap::PostMessage(new Message(
-      port_id, buffer, writer.BytesWritten(), Message::kNormalPriority));
+      port_id, buffer, writer.BytesWritten(), priority));
+}
+
+
+DART_EXPORT bool Dart_PostCObject(Dart_Port port_id, Dart_CObject* message) {
+  return PostCObject(port_id, message, Message::kNormalPriority);
+}
+
+
+DART_EXPORT bool Dart_PostOOBCObject(Dart_Port port_id, Dart_CObject* message) {
+  return PostCObject(port_id, message, Message::kOOBPriority);
 }