Rename rendering/render_*.dart to rendering/*.dart

sky/sdk/lib/framework/components2/icon_button.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 '../fn2.dart';
+import '../rendering/box.dart';
 import 'icon.dart';
 
 class IconButton extends Component {
   static Style _style = new Style('''
     padding: 8px;''');
 
   String icon;
   GestureEventListener onGestureTap;
 
   IconButton({ String icon: '', this.onGestureTap })
     : super(key: icon), icon = icon;
 
   UINode build() {
     return new EventListenerNode(
       new StyleNode(new Icon(type: icon, size: 24), _style),
       onGestureTap: onGestureTap);
   }
 }