Rationalize Dart mojo and sky package structure

mojo/public/dart/lib/src/handle_watcher.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 internal;
 
 // The MojoHandleWatcher sends a stream of events to application isolates that
 // register Mojo handles with it. Application isolates make the following calls:
 //
 // add(handle, port, signals) - Instructs the MojoHandleWatcher isolate to add
@@ skipping 333 matching lines @@
 
   static int remove(int mojoHandle) {
     return _sendControlData(mojoHandle, null, _encodeCommand(REMOVE));
   }
 
   static int timer(Object ignored, SendPort port, int deadline) {
     // The deadline will be unwrapped before sending to the handle watcher.
     return _sendControlData(deadline, port, _encodeCommand(TIMER));
   }
 }