Use package:sky imports consistently

sky/sdk/lib/widgets/icon.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 '../mojo/asset_bundle.dart';
-import 'basic.dart';
-import 'theme.dart';
-import 'widget.dart';
+import 'package:sky/mojo/asset_bundle.dart';
+import 'package:sky/widgets/basic.dart';
+import 'package:sky/widgets/theme.dart';
+import 'package:sky/widgets/widget.dart';
 
 enum IconThemeColor { white, black }
 
 class IconThemeData {
   const IconThemeData({ this.color });
   final IconThemeColor color;
 }
 
 class IconTheme extends Inherited {
 
@@ skipping 62 matching lines @@
     // TODO(eseidel): This clearly isn't correct.  Not sure what would be.
     // Should we use the ios images on ios?
     String density = 'drawable-xxhdpi';
     return new AssetImage(
       bundle: _iconBundle,
       name: '${category}/${density}/ic_${subtype}_${colorSuffix}_${size}dp.png',
       size: new Size(size.toDouble(), size.toDouble())
     );
   }
 }