Rationalize Dart mojo and sky package structure

mojo/public/dart/lib/src/control_message.dart

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 part of bindings;
 
 // Handles InterfaceControlMessages for a stub.
 class ControlMessageHandler {
   static bool isControlMessage(ServiceMessage message) =>
       _isRun(message) || _isRunOrClose(message);
@@ skipping 41 matching lines @@
     // Grab required version.
     var requiredVersion = params.requireVersion.version;
     if (interface_version >= requiredVersion) {
       // Stub meets the requirements.
       return;
     }
     // Stub does not implement required version. Close the pipe immediately.
     stub.close(immediate: true);
   }
 }