Rationalize Dart mojo and sky package structure

services/dart/dart_apptests/echo_apptests.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.
 
 library echo_apptests;
 
 import 'dart:async';
 
 import 'package:apptest/apptest.dart';
 import 'package:mojom/dart/test/echo_service.mojom.dart';
-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';
 
 echoApptests(Application application, String url) {
   group('Echo Service Apptests', () {
     test('String', () async {
       var echoProxy = new EchoServiceProxy.unbound();
       application.connectToService("mojo:dart_echo", echoProxy);
 
       var v = await echoProxy.ptr.echoString("foo");
       expect(v.value, equals("foo"));
 
@@ skipping 55 matching lines @@
         throw 'unreachable';
       }, onError: (e) {
         expect(e is ProxyCloseException, isTrue);
       });
 
       return new Future.delayed(
           new Duration(milliseconds: 10), () => echoProxy.close());
     });
   });
 }