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

sky/sdk/lib/framework/rendering/block.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 'render_box.dart';
-import 'render_node.dart';
+import 'box.dart';
+import 'node.dart';
 
 class BlockParentData extends BoxParentData with ContainerParentDataMixin<RenderBox> { }
 
 class RenderBlock extends RenderBox with ContainerRenderNodeMixin<RenderBox, BlockParentData>,
                                          RenderBoxContainerDefaultsMixin<RenderBox, BlockParentData> {
   // lays out RenderBox children in a vertical stack
   // uses the maximum width provided by the parent
   // sizes itself to the height of its child stack
 
   void setParentData(RenderBox child) {
@@ skipping 42 matching lines @@
   void hitTestChildren(HitTestResult result, { sky.Point position }) {
     defaultHitTestChildren(result, position: position);
   }
 
   void paint(RenderNodeDisplayList canvas) {
     defaultPaint(canvas);
   }
 
 }