Make rebuilding faster

sky/sdk/lib/widgets/widget.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 'dart:collection';
 import 'dart:mirrors';
 import 'dart:sky' as sky;
 
 import '../base/hit_test.dart';
@@ skipping 28 matching lines @@
   String _key;
   String get key => _key;
 
   Widget _parent;
   Widget get parent => _parent;
 
   bool _mounted = false;
   bool _wasMounted = false;
   bool get mounted => _mounted;
   static bool _notifyingMountStatus = false;
-  static Set<Widget> _mountedChanged = new HashSet<Widget>();
+  static List<Widget> _mountedChanged = new List<Widget>();
 
   void setParent(Widget newParent) {
     assert(!_notifyingMountStatus);
     _parent = newParent;
     if (newParent == null) {
       if (_mounted) {
         _mounted = false;
         _mountedChanged.add(this);
       }
     } else {
@@ skipping 74 matching lines @@
 
     if (node == null) {
       // the child in this slot has gone away
       assert(oldNode.mounted);
       oldNode.detachRoot();
       removeChild(oldNode);
       assert(!oldNode.mounted);
       return null;
     }
 
-    if (oldNode != null &&
-        oldNode.runtimeType == node.runtimeType &&
-        oldNode.key == node.key &&
-        node._retainStatefulNodeIfPossible(oldNode)) {
-      assert(oldNode.mounted);
-      assert(!node.mounted);
-      oldNode._sync(node, slot);
-      assert(oldNode.root is RenderObject);
-      return oldNode;
-    }
-
-    if (oldNode != null &&
-        (oldNode.runtimeType != node.runtimeType || oldNode.key != node.key)) {
-      assert(oldNode.mounted);
-      oldNode.detachRoot();
-      removeChild(oldNode);
-      oldNode = null;
+    if (oldNode != null) {
+      if (oldNode.runtimeType == node.runtimeType && oldNode.key == node.key) {
+        if (node._retainStatefulNodeIfPossible(oldNode)) {
+          assert(oldNode.mounted);
+          assert(!node.mounted);
+          oldNode._sync(node, slot);
+          assert(oldNode.root is RenderObject);
+          return oldNode;
+        }
+      } else {
+        assert(oldNode.mounted);
+        oldNode.detachRoot();
+        removeChild(oldNode);
+        oldNode = null;
+      }
     }
 
     assert(!node.mounted);
     node.setParent(this);
     node._sync(oldNode, slot);
     assert(node.root is RenderObject);
     return node;
   }
 
   String toString() {
@@ skipping 828 matching lines @@
     if (root.parent == null) {
       // we haven't attached it yet
       assert(_container.child == null);
       _container.child = root;
     }
     assert(root.parent == _container);
   }
 
   Widget build() => builder();
 }