Split layout2.dart into several files

sky/tests/raw/render_flex.dart

Index: sky/tests/raw/render_flex.dart
diff --git a/sky/tests/raw/render_flex.dart b/sky/tests/raw/render_flex.dart
index 97ea459c43d9223dc3207264874f43f8cccfc7b3..5cc95895e2ba906769b59876a9f7c801919a8a24 100644
--- a/sky/tests/raw/render_flex.dart
+++ b/sky/tests/raw/render_flex.dart
@@ -6,7 +6,9 @@ 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;
@@ -41,13 +43,13 @@ void main() {
   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;
     }