Rename BlockContainer, StackContainer, and FlexContainer

sky/sdk/lib/framework/components2/popup_menu.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 '../animation/animated_value.dart';
 import '../fn2.dart';
 import '../theme2/colors.dart';
 import '../theme2/shadows.dart';
 import 'animated_component.dart';
 import 'dart:async';
@@ skipping 103 matching lines @@
     }));
 
     // inlineStyle: _inlineStyle(),
     return new ShrinkWrapWidth(
       child: new Container(
         padding: const EdgeDims.all(8.0),
         decoration: new BoxDecoration(
           backgroundColor: Grey[50],
           borderRadius: 2.0,
           boxShadow: Shadow[level]),
-        child: new BlockContainer(children: children)
+        child: new Block(children)
       )
     );
   }
 
 }