Split layout2.dart into several files

sky/tests/raw/render_flex.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 '../resources/third_party/unittest/unittest.dart';
 import '../resources/unit.dart';
 import 'dart:sky' as sky;
 import 'package:sky/framework/app.dart';
-import 'package:sky/framework/layout2.dart';
+import 'package:sky/framework/rendering/render_block.dart';
+import 'package:sky/framework/rendering/render_box.dart';
+import 'package:sky/framework/rendering/render_flex.dart';
 
 class RenderSolidColor extends RenderDecoratedBox {
   final sky.Size desiredSize;
   final int backgroundColor;
 
   RenderSolidColor(int backgroundColor, { this.desiredSize: const sky.Size.infinite() })
       : backgroundColor = backgroundColor,
         super(decoration: new BoxDecoration(backgroundColor: backgroundColor)) {
   }
 
@@ skipping 14 matching lines @@
 }
 
 AppView app;
 
 void main() {
   initUnit();
 
   test("should flex", () {
     RenderFlex flexRoot = new RenderFlex(direction: FlexDirection.Vertical);
 
-    RenderNode root = new RenderDecoratedBox(
+    RenderDecoratedBox root = new RenderDecoratedBox(
       decoration: new BoxDecoration(backgroundColor: 0xFF000000),
       child: flexRoot
     );
 
     void addFlexChildSolidColor(RenderFlex parent, int backgroundColor, { int flex: 0 }) {
-      RenderNode child = new RenderSolidColor(backgroundColor);
+      RenderSolidColor child = new RenderSolidColor(backgroundColor);
       parent.add(child);
       child.parentData.flex = flex;
     }
 
     // Yellow bar at top
     addFlexChildSolidColor(flexRoot, 0xFFFFFF00, flex: 1);
 
     // Turquoise box
     flexRoot.add(new RenderSolidColor(0x7700FFFF, desiredSize: new sky.Size(100.0, 100.0)));
 
@@ skipping 25 matching lines @@
     decoratedRow.parentData.flex = 3;
 
     app = new AppView(root);
 
     expect(root.size.width, equals(sky.view.width));
     expect(root.size.height, equals(sky.view.height));
     expect(renderBlock.size.width, equals(sky.view.width - 20.0));
 
   });
 }