[Effen] basic layout container class for custom layout

sky/framework/components/fixed_height_scrollable.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/scroll_behavior.dart';
 import '../debug/tracing.dart';
 import '../fn.dart';
 import 'dart:math' as math;
 import 'dart:sky' as sky;
 import 'dart:async';
 import 'scrollable.dart';
+import '../layouts/block.dart';
 
 abstract class FixedHeightScrollable extends Scrollable {
   static final Style _style = new Style('''
     overflow: hidden;
     position: relative;
     will-change: transform;'''
   );
 
   static final Style _scrollAreaStyle = new Style('''
     position:relative;
@@ skipping 55 matching lines @@
         itemNumber = math.max(0, (drawStart / _itemHeight).floor());
 
         transformStyle =
             'transform: translateY(${(alignmentDelta).toStringAsFixed(2)}px)';
       }
     }
 
     return new Container(
       style: _style,
       children: [
-        new Container(
+        new BlockLayout(
           style: _scrollAreaStyle,
           inlineStyle: transformStyle,
           children: buildItems(itemNumber, drawCount)
         )
       ]
     );
   }
 }