Rationalize Dart mojo and sky package structure

mojo/public/dart/lib/src/message_pipe.dart

 // Copyright 2014 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 core;
 
 class MojoMessagePipeReadResult {
   final MojoResult status;
   final int bytesRead;
   final int handlesRead;
@@ skipping 128 matching lines @@
     MojoHandle end1 = new MojoHandle(result[1]);
     MojoHandle end2 = new MojoHandle(result[2]);
     MojoMessagePipe pipe = new MojoMessagePipe._();
     pipe.endpoints = new List(2);
     pipe.endpoints[0] = new MojoMessagePipeEndpoint(end1);
     pipe.endpoints[1] = new MojoMessagePipeEndpoint(end2);
     pipe.status = new MojoResult(result[0]);
     return pipe;
   }
 }