Rationalize Dart mojo and sky package structure

mojo/dart/embedder/test/dart_to_cpp_tests.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 'dart:typed_data';
 
 import 'package:mojom/dart_to_cpp/dart_to_cpp.mojom.dart';
-import 'package:mojo/public/dart/bindings.dart' as bindings;
-import 'package:mojo/public/dart/core.dart' as core;
+import 'package:mojo/bindings.dart' as bindings;
+import 'package:mojo/core.dart' as core;
 
 class DartSideImpl implements DartSide {
   static const int BAD_VALUE = 13;
   static const int ELEMENT_BYTES = 1;
   static const int CAPACITY_BYTES = 64;
 
   DartSideStub _stub;
   CppSideProxy cppSide;
 
   Uint8List _sampleData;
@@ skipping 89 matching lines @@
 main(List args) {
   assert(args.length == 2);
   int mojoHandle = args[0];
   var rawHandle = new core.MojoHandle(mojoHandle);
   var endpoint = new core.MojoMessagePipeEndpoint(rawHandle);
   var dartSide = new DartSideImpl(endpoint);
   dartSide.future.then((_) {
     print('Success');
   });
 }