Improve stocks2 performance

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 39 matching lines @@
       assert(newParent._mounted);
       if (_parent._mounted != _mounted) {
         _mounted = _parent._mounted;
         _mountedChanged.add(this);
       }
     }
   }
 
   static void _notifyMountStatusChanged() {
     try {
+      sky.tracing.begin("Widget._notifyMountStatusChanged");
       _notifyingMountStatus = true;
       for (Widget node in _mountedChanged) {
         if (node._wasMounted != node._mounted) {
           if (node._mounted)
             node.didMount();
           else
             node.didUnmount();
           node._wasMounted = node._mounted;
         }
       }
       _mountedChanged.clear();
     } finally {
       _notifyingMountStatus = false;
+      sky.tracing.end("Widget._notifyMountStatusChanged");
     }
   }
   void didMount() { }
   void didUnmount() { }
 
   RenderObject _root;
   RenderObject get root => _root;
 
   // Subclasses which implements Nodes that become stateful may return true
   // if the |old| node has become stateful and should be retained.
@@ skipping 344 matching lines @@
 
   Widget build();
 
 }
 
 Set<Component> _dirtyComponents = new Set<Component>();
 bool _buildScheduled = false;
 bool _inRenderDirtyComponents = false;
 
 void _buildDirtyComponents() {
-  //_tracing.begin('fn::_buildDirtyComponents');
-
   Stopwatch sw;
   if (_shouldLogRenderDuration)
     sw = new Stopwatch()..start();
 
   try {
+    sky.tracing.begin('Widgets._buildDirtyComponents');
     _inRenderDirtyComponents = true;
 
     List<Component> sortedDirtyComponents = _dirtyComponents.toList();
     sortedDirtyComponents.sort((Component a, Component b) => a._order - b._order);
     for (var comp in sortedDirtyComponents) {
       comp._buildIfDirty();
     }
 
     _dirtyComponents.clear();
     _buildScheduled = false;
   } finally {
     _inRenderDirtyComponents = false;
+    sky.tracing.end('Widgets._buildDirtyComponents');
   }
 
   Widget._notifyMountStatusChanged();
 
   if (_shouldLogRenderDuration) {
     sw.stop();
     print('Render took ${sw.elapsedMicroseconds} microseconds');
   }
-
-  //_tracing.end('fn::_buildDirtyComponents');
 }
 
 void _scheduleComponentForRender(Component c) {
   assert(!_inRenderDirtyComponents);
   _dirtyComponents.add(c);
 
   if (!_buildScheduled) {
     _buildScheduled = true;
     new Future.microtask(_buildDirtyComponents);
   }
@@ skipping 253 matching lines @@
       ensureOldIdMap();
       oldNode = oldNodeIdMap[currentNode.key];
       if (oldNode == null)
         return false;
 
       oldNodeIdMap[currentNode.key] = null; // mark it reordered
       assert(root is ContainerRenderObjectMixin);
       assert(old.root is ContainerRenderObjectMixin);
       assert(oldNode.root != null);
 
-      (old.root as ContainerRenderObjectMixin).remove(oldNode.root); // TODO(ianh): Remove cast once the analyzer is cleverer
-      root.add(oldNode.root, before: nextSibling);
+      if (old.root == root) {
+        root.move(oldNode.root, before: nextSibling);
+      } else {
+        (old.root as ContainerRenderObjectMixin).remove(oldNode.root); // TODO(ianh): Remove cast once the analyzer is cleverer
+        root.add(oldNode.root, before: nextSibling);
+      }
 
       return true;
     }
 
     // Scan forwards, this time we may re-order;
     nextSibling = root.firstChild;
     while (startIndex < endIndex && oldStartIndex < oldEndIndex) {
       currentNode = children[startIndex];
       oldNode = oldChildren[oldStartIndex];
 
@@ skipping 160 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();
 }