Improve the padding and sizing of popup menus.

sky/sdk/lib/widgets/basic.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' as sky;
 
 import 'package:vector_math/vector_math.dart';
 
 import '../painting/text_style.dart';
 import '../rendering/block.dart';
@@ skipping 213 matching lines @@
   RenderConstrainedBox createNode() => new RenderConstrainedBox(additionalConstraints: constraints);
 
   void syncRenderObject(ConstrainedBox old) {
     super.syncRenderObject(old);
     root.additionalConstraints = constraints;
   }
 
 }
 
 class ShrinkWrapWidth extends OneChildRenderObjectWrapper {
-  ShrinkWrapWidth({ String key, Widget child })
-    : super(key: key, child: child);
+
+  ShrinkWrapWidth({
+    String key,
+    this.stepWidth,
+    this.stepHeight,
+    Widget child
+  }): super(key: key, child: child);
 
   RenderShrinkWrapWidth get root => super.root;
+
+  final double stepWidth;
+  final double stepHeight;
+
   RenderShrinkWrapWidth createNode() => new RenderShrinkWrapWidth();
+
+  void syncRenderObject(ShrinkWrapWidth old) {
+    super.syncRenderObject(old);
+    root.stepWidth = stepWidth;
+    root.stepHeight = stepHeight;
+  }
+
 }
 
 class SizeObserver extends OneChildRenderObjectWrapper {
 
   SizeObserver({ String key, this.callback, Widget child })
     : super(key: key, child: child);
 
   RenderSizeObserver get root => super.root;
   final SizeChangedCallback callback;
 
@@ skipping 240 matching lines @@
   }
 
   void remove() {
     RenderObjectWrapper ancestor = findAncestor(RenderObjectWrapper);
     assert(ancestor is RenderObjectWrapper);
     ancestor.detachChildRoot(this);
     super.remove();
   }
 
 }