Add some basic tests for the material buttons

Specifically, RaisedButton, FlatButton, and FloatingActionButton. These just
test that these classes work in their default configurations.

R=ianh@google.com, jackson@chromium.org

Review URL: https://codereview.chromium.org/1193453005.

tests/resources/display_list.dart

 
+import 'dart:async';
 import 'dart:sky' as sky;
 import "dart:sky.internals" as internals;
 
+import 'package:sky/widgets/basic.dart';
 import 'package:sky/rendering/box.dart';
 import 'package:sky/rendering/object.dart';
 
@@ -156,3 +158,29 @@ class TestRenderView extends RenderView {
   }
 
 }
+
+class TestApp extends App {
+  TestApp({
+    this.builder,
+    RenderView renderViewOverride
+  }) : super(renderViewOverride: renderViewOverride);
+
+  Function builder;
+
+  Widget build() {
+    return builder();
+  }
+}
+
+class WidgetTester {
+  TestRenderView renderView = new TestRenderView();
+
+  Future test(Function builder) {
+    new TestApp(renderViewOverride: renderView, builder: builder);
+    return new Future.microtask(renderView.checkFrame);
+  }
+
+  Future endTest() {
+    return new Future.microtask(renderView.endTest);
+  }
+}

tests/widgets/buttons-expected.txt

+CONSOLE: TestRenderView enabled
+CONSOLE: 
+PAINT FOR FRAME #1 ----------------------------------------------
+1 | TestDisplayList() constructor: 800.0 x 600.0
+------------------------------------------------------------------------
+CONSOLE: 
+PAINT FOR FRAME #2 ----------------------------------------------
+2 | TestDisplayList() constructor: 800.0 x 600.0
+2 | paintChild RenderPositionedBox at Point(0.0, 0.0)
+2 |  | TestDisplayList() constructor: 800.0 x 600.0
+2 |  | paintChild RenderPadding at Point(348.0, 274.0)
+2 |  |  | TestDisplayList() constructor: 800.0 x 600.0
+2 |  |  | paintChild RenderConstrainedBox at Point(8.0, 8.0)
+2 |  |  |  | TestDisplayList() constructor: 800.0 x 600.0
+2 |  |  |  | drawRRect(Instance of 'RRect', Paint(Color(0xffe0e0e0)))
+2 |  |  |  | paintChild RenderPositionedBox at Point(8.0, 0.0)
+2 |  |  |  |  | TestDisplayList() constructor: 800.0 x 600.0
+2 |  |  |  |  | paintChild RenderParagraph at Point(6.0, 10.0)
+2 |  |  |  |  |  | TestDisplayList() constructor: 800.0 x 600.0
+------------------------------------------------------------------------
+CONSOLE: 
+PAINT FOR FRAME #3 ----------------------------------------------
+3 | TestDisplayList() constructor: 800.0 x 600.0
+3 | paintChild RenderPositionedBox at Point(0.0, 0.0)
+3 |  | TestDisplayList() constructor: 800.0 x 600.0
+3 |  | paintChild RenderPadding at Point(348.0, 274.0)
+3 |  |  | TestDisplayList() constructor: 800.0 x 600.0
+3 |  |  | paintChild RenderConstrainedBox at Point(8.0, 8.0)
+3 |  |  |  | TestDisplayList() constructor: 800.0 x 600.0
+3 |  |  |  | drawRRect(Instance of 'RRect', Paint(Color(0xfffafafa)))
+3 |  |  |  | paintChild RenderPositionedBox at Point(8.0, 0.0)
+3 |  |  |  |  | TestDisplayList() constructor: 800.0 x 600.0
+3 |  |  |  |  | paintChild RenderParagraph at Point(6.0, 10.0)
+3 |  |  |  |  |  | TestDisplayList() constructor: 800.0 x 600.0
+------------------------------------------------------------------------
+CONSOLE: 
+PAINT FOR FRAME #4 ----------------------------------------------
+4 | TestDisplayList() constructor: 800.0 x 600.0
+4 | paintChild RenderPositionedBox at Point(0.0, 0.0)
+4 |  | TestDisplayList() constructor: 800.0 x 600.0
+4 |  | paintChild RenderDecoratedBox at Point(372.0, 272.0)
+4 |  |  | TestDisplayList() constructor: 800.0 x 600.0
+4 |  |  | drawCircle(28.0, 28.0, 28.0, Paint(Color(0xfff44336)))
+4 |  |  | saveLayer(Rect.fromLTRB(0.0, 0.0, 56.0, 56.0), Paint(Color(0xff000000)))
+4 |  |  | clipPath(Instance of 'Path')
+4 |  |  | paintChild RenderParagraph at Point(22.0, 20.0)
+4 |  |  |  | TestDisplayList() constructor: 800.0 x 600.0
+4 |  |  | restore
+------------------------------------------------------------------------
+PAINTED 4 FRAMES

tests/widgets/buttons.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 'package:sky/widgets/basic.dart';
+import 'package:sky/widgets/flat_button.dart';
+import 'package:sky/widgets/floating_action_button.dart';
+import 'package:sky/widgets/raised_button.dart';
+
+import '../resources/display_list.dart';
+
+main() async {
+  WidgetTester tester = new WidgetTester();
+
+  await tester.test(() {
+    return new Center(child: new RaisedButton(child: new Text("ENGAGE")));
+  });
+
+  await tester.test(() {
+    return new Center(child: new FlatButton(child: new Text("ENGAGE")));
+  });
+
+  await tester.test(() {
+    return new Center(child: new FloatingActionButton(child: new Text("+")));
+  });
+
+  await tester.endTest();
+}