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

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 5a019fe8c4b430402338976fba74bbac82f54e83..60d0cb82cbfe4af43513090011e8127dd0271fb2 100644
--- a/sky/tests/raw/render_flex.dart
+++ b/sky/tests/raw/render_flex.dart
@@ -7,9 +7,9 @@ import '../resources/unit.dart';
 import '../resources/display_list.dart';
 import 'dart:sky' as sky;
 import 'package:sky/framework/app.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';
+import 'package:sky/framework/rendering/block.dart';
+import 'package:sky/framework/rendering/box.dart';
+import 'package:sky/framework/rendering/flex.dart';
 
 class RenderSolidColor extends RenderDecoratedBox {
   final sky.Size desiredSize;