Use package:sky imports consistently

sky/sdk/lib/mojo/asset_bundle.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.
 
 import 'dart:async';
 import 'dart:sky' as sky;
 import 'dart:sky.internals' as internals;
 import 'dart:typed_data';
 
 import 'package:mojo/core.dart' as core;
 import 'package:mojom/mojo/asset_bundle/asset_bundle.mojom.dart';
-
-import 'net/fetch.dart';
-import 'net/image_cache.dart' as image_cache;
-import 'shell.dart' as shell;
+import 'package:sky/mojo/net/fetch.dart';
+import 'package:sky/mojo/net/image_cache.dart' as image_cache;
+import 'package:sky/mojo/shell.dart' as shell;
 
 abstract class AssetBundle {
   void close();
   Future<sky.Image> loadImage(String key);
   Future<String> loadString(String key);
 }
 
 class NetworkAssetBundle extends AssetBundle {
   NetworkAssetBundle(Uri baseUrl) : _baseUrl = baseUrl;
 
@@ skipping 62 matching lines @@
   try {
     AssetBundleProxy bundle = new AssetBundleProxy.fromHandle(
         new core.MojoHandle(internals.takeRootBundleHandle()));
     return new MojoAssetBundle(bundle);
   } catch (e) {
     return null;
   }
 }
 
 final AssetBundle rootBundle = _initRootBundle();