Remove Material's opinion about background colours, since in fact the background colour varies dram…

sky/sdk/example/widgets/sector.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:math' as math;
 
 import 'package:sky/rendering/box.dart';
 import 'package:sky/rendering/flex.dart';
 import 'package:sky/rendering/sky_binding.dart';
 import 'package:sky/theme/colors.dart' as colors;
@@ skipping 61 matching lines @@
     });
   }
 
   Widget build() {
     return new Theme(
       data: new ThemeData.light(primary: colors.Blue, darkToolbar: true),
       child: new Scaffold(
         toolbar: new ToolBar(
             center: new Text('Sector Layout in a Widget Tree')),
         body: new Material(
+          color: colors.Grey[50],
           edge: MaterialEdge.canvas,
           child: new Flex([
               new Container(
                 padding: new EdgeDims.symmetric(horizontal: 8.0, vertical: 25.0),
                 child: new Flex([
                     new RaisedButton(
                       enabled: enabledAdd,
                       child: new ShrinkWrapWidth(
                         child: new Flex([
                           new Container(
@@ skipping 44 matching lines @@
   }
 }
 
 void main() {
   runApp(new SectorApp());
   SkyBinding.instance.onFrame = () {
     // uncomment this for debugging:
     // SkyBinding.instance.debugDumpRenderTree();
   };
 }