Add a very simple RenderParagraph example using LayoutRoot.

I'm sure we'll want something more sophisticated in the near future.

Next step is to actually animate this updating layout.

R=ianh@google.com

Review URL: https://codereview.chromium.org/1150183005

examples/raw/render_paragraph.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:sky';
+import 'package:sky/framework/app.dart';
+import 'package:sky/framework/layout2.dart';
+
+class RenderParagraph extends RenderDecoratedBox {
+  final String text;
+  LayoutRoot _layoutRoot = new LayoutRoot();
+  Document _document;
+
+  RenderParagraph(String this.text) :
+   super(new BoxDecoration(backgroundColor: 0xFFFFFFFF)) {
+    _document = new Document();
+    _layoutRoot.rootElement = _document.createElement('p');
+    _layoutRoot.rootElement.appendChild(_document.createText(this.text));
+  }
+
+  void performLayout() {
+    _layoutRoot.maxWidth = constraints.maxWidth;
+    _layoutRoot.minWidth = constraints.minWidth;
+    _layoutRoot.layout();
+    width = _layoutRoot.rootElement.width;
+    height = _layoutRoot.rootElement.height;
+  }
+
+  void hitTestChildren(HitTestResult result, { double x, double y }) {
+    // defaultHitTestChildren(result, x: x, y: y);
+  }
+
+  void paint(RenderNodeDisplayList canvas) {
+    super.paint(canvas);
+    _layoutRoot.paint(canvas);
+  }
+}
+
+class RenderSolidColor extends RenderDecoratedBox {
+  final double desiredHeight;
+  final double desiredWidth;
+  final int backgroundColor;
+
+  RenderSolidColor(int backgroundColor, { this.desiredHeight: double.INFINITY,
+                                          this.desiredWidth: double.INFINITY })
+      : backgroundColor = backgroundColor,
+        super(new BoxDecoration(backgroundColor: backgroundColor));
+
+  BoxDimensions getIntrinsicDimensions(BoxConstraints constraints) {
+    return new BoxDimensions.withConstraints(constraints,
+                                             height: desiredHeight,
+                                             width: desiredWidth);
+  }
+
+  void performLayout() {
+    width = constraints.constrainWidth(desiredWidth);
+    height = constraints.constrainHeight(desiredHeight);
+  }
+
+  void handlePointer(PointerEvent event) {
+    if (event.type == 'pointerdown')
+      decoration = new BoxDecoration(backgroundColor: 0xFFFF0000);
+    else if (event.type == 'pointerup')
+      decoration = new BoxDecoration(backgroundColor: backgroundColor);
+  }
+}
+
+AppView app;
+
+void main() {
+  var root = new RenderFlex(
+      direction: FlexDirection.Vertical,
+      decoration: new BoxDecoration(backgroundColor: 0xFF000000));
+
+  RenderNode child = new RenderSolidColor(0xFFFFFF00);
+  root.add(child);
+  child.parentData.flex = 2;
+
+  // The internet is a beautiful place.  https://baconipsum.com/
+  String meatyString = """Bacon ipsum dolor amet ham fatback tri-tip, prosciutto
+porchetta bacon kevin meatball meatloaf pig beef ribs chicken. Brisket ribeye
+andouille leberkas capicola meatloaf. Chicken pig ball tip pork picanha bresaola
+alcatra. Pork pork belly alcatra, flank chuck drumstick biltong doner jowl.
+Pancetta meatball tongue tenderloin rump tail jowl boudin.""";
+
+  child = new RenderParagraph(meatyString);
+  root.add(child);
+  child.parentData.flex = 1;
+
+  app = new AppView(root);
+}