Rationalize Dart mojo and sky package structure

mojo/public/dart/lib/src/buffer.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 MojoSharedBuffer {
   static const int CREATE_FLAG_NONE = 0;
   static const int DUPLICATE_FLAG_NONE = 0;
   static const int MAP_FLAG_NONE = 0;
@@ skipping 65 matching lines @@
     return status;
   }
 
   MojoResult unmap() {
     int r = MojoSharedBufferNatives.Unmap(mapping);
     status = new MojoResult(r);
     mapping = null;
     return status;
   }
 }