Rename UINode to Widget.

sky/tests/framework/stocks.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:async';
 
 import 'package:sky/app/view.dart';
-import 'package:sky/widgets/ui_node.dart';
+import 'package:sky/widgets/widget.dart';
 
 import '../../examples/stocks2/lib/stock_app.dart';
 import '../resources/display_list.dart';
 import '../resources/third_party/unittest/unittest.dart';
 import '../resources/unit.dart';
 
 void main() {
   initUnit();
 
   TestRenderView testRenderView = new TestRenderView();
 
   test("launching stock app", () {
     new StocksApp(renderViewOverride: testRenderView);
     new Future.microtask(testRenderView.checkFrame);
   });
 }