Introduce sky.Sky.zero

sky/sdk/lib/framework/rendering/box.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:math' as math;
 import 'dart:sky' as sky;
 import 'dart:typed_data';
 import 'object.dart';
 import 'package:vector_math/vector_math.dart';
 import 'package:sky/framework/net/image_cache.dart' as image_cache;
@@ skipping 107 matching lines @@
     if (child.parentData is! BoxParentData)
       child.parentData = new BoxParentData();
   }
 
   // override this to report what dimensions you would have if you
   // were laid out with the given constraints this can walk the tree
   // if it must, but it should be as cheap as possible; just get the
   // dimensions and nothing else (e.g. don't calculate hypothetical
   // child positions if they're not needed to determine dimensions)
   Size getIntrinsicDimensions(BoxConstraints constraints) {
-    return constraints.constrain(new Size(0.0, 0.0));
+    return constraints.constrain(Size.zero);
   }
 
   BoxConstraints get constraints => super.constraints as BoxConstraints;
   void performResize() {
     // default behaviour for subclasses that have sizedByParent = true
-    size = constraints.constrain(new Size(0.0, 0.0));
+    size = constraints.constrain(Size.zero);
     assert(size.height < double.INFINITY);
     assert(size.width < double.INFINITY);
   }
   void performLayout() {
     // descendants have to either override performLayout() to set both
     // width and height and lay out children, or, set sizedByParent to
     // true so that performResize()'s logic above does its thing.
     assert(sizedByParent);
   }
 
   bool hitTest(HitTestResult result, { Point position }) {
     hitTestChildren(result, position: position);
     result.add(this);
     return true;
   }
   void hitTestChildren(HitTestResult result, { Point position }) { }
 
-  Size size = new Size(0.0, 0.0);
+  Size size = Size.zero;
 
   String debugDescribeSettings(String prefix) => '${super.debugDescribeSettings(prefix)}${prefix}size: ${size}\n';
 }
 
 abstract class RenderProxyBox extends RenderBox with RenderObjectWithChildMixin<RenderBox> {
   RenderProxyBox(RenderBox child) {
     this.child = child;
   }
 
   Size getIntrinsicDimensions(BoxConstraints constraints) {
@@ skipping 552 matching lines @@
 
 class RenderView extends RenderObject with RenderObjectWithChildMixin<RenderBox> {
 
   RenderView({
     RenderBox child,
     this.timeForRotation: const Duration(microseconds: 83333)
   }) {
     this.child = child;
   }
 
-  Size _size = new Size(0.0, 0.0);
+  Size _size = Size.zero;
   double get width => _size.width;
   double get height => _size.height;
 
   int _orientation; // 0..3
   int get orientation => _orientation;
   Duration timeForRotation;
 
   ViewConstraints get constraints => super.constraints as ViewConstraints;
   bool get sizedByParent => true;
   void performResize() {
@@ skipping 63 matching lines @@
 
   void defaultPaint(RenderObjectDisplayList canvas) {
     RenderBox child = firstChild;
     while (child != null) {
       assert(child.parentData is ParentDataType);
       canvas.paintChild(child, child.parentData.position);
       child = child.parentData.nextSibling;
     }
   }
 }