Rationalize Dart mojo and sky package structure

services/dart/test/echo/main.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.
 
 import 'dart:async';
 
-import 'package:mojo/public/dart/application.dart';
-import 'package:mojo/public/dart/bindings.dart';
-import 'package:mojo/public/dart/core.dart';
+import 'package:mojo/application.dart';
+import 'package:mojo/bindings.dart';
+import 'package:mojo/core.dart';
 import 'package:mojom/dart/test/echo_service.mojom.dart';
 
 class EchoServiceImpl implements EchoService {
   EchoServiceStub _stub;
   Application _application;
 
   EchoServiceImpl(this._application, MojoMessagePipeEndpoint endpoint) {
     _stub = new EchoServiceStub.fromEndpoint(endpoint, this);
   }
 
@@ skipping 26 matching lines @@
 }
 
 main(List args) {
   MojoHandle appHandle = new MojoHandle(args[0]);
   String url = args[1];
   new EchoApplication.fromHandle(appHandle)
     ..onError = (() {
       assert(MojoHandle.reportLeakedHandles());
     });
 }