Refactoring to support dark theme better

sky/sdk/lib/widgets/drawer.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:sky' as sky;
 
 import '../animation/animation_performance.dart';
 import '../animation/curves.dart';
-import '../theme/colors.dart';
 import '../theme/shadows.dart';
 import 'animated_component.dart';
 import 'basic.dart';
+import 'theme.dart';
 
 // TODO(eseidel): Draw width should vary based on device size:
 // http://www.google.com/design/spec/layout/structure.html#structure-side-nav
 
 // Mobile:
 // Width = Screen width − 56 dp
 // Maximum width: 320dp
 // Maximum width applies only when using a left nav. When using a right nav,
 // the panel can cover the full width of the screen.
 
@@ skipping 98 matching lines @@
     Color maskColor = new Color.fromARGB((0x7F * scaler).floor(), 0, 0, 0);
 
     var mask = new Listener(
       child: new Container(decoration: new BoxDecoration(backgroundColor: maskColor)),
       onGestureTap: controller.handleMaskTap
     );
 
     Widget content = controller.position.build(
       new Container(
         decoration: new BoxDecoration(
-          backgroundColor: Grey[50],
+          backgroundColor: Theme.of(this).canvasColor,
           boxShadow: shadows[level]),
         width: _kWidth,
         child: new Block(children)
       ));
 
     return new Listener(
       child: new Stack([ mask, content ]),
       onPointerDown: controller.handlePointerDown,
       onPointerMove: controller.handlePointerMove,
       onPointerUp: controller.handlePointerUp,
       onPointerCancel: controller.handlePointerCancel,
       onGestureFlingStart: controller.handleFlingStart
     );
   }
 
 }