ui/list.js: prevent from position calculation with wrong position.

chrome/browser/resources/shared/js/cr/ui/list.js

 // Copyright (c) 2012 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.
 
 // require: array_data_model.js
 // require: list_selection_model.js
 // require: list_selection_controller.js
 // require: list_item.js
 
 /**
@@ skipping 1030 matching lines @@
       var dataModel = this.dataModel;
       if (!dataModel) {
         this.cachedItems_ = {};
         this.firstIndex_ = 0;
         this.lastIndex_ = 0;
         this.remainingSpace_ = true;
         this.mergeItems(0, 0, {}, {});
         return;
       }
 
+      // Save the previous positions before any manipulation of elements.
+      var scrollTop = this.scrollTop;
+      var clientHeight = this.clientHeight;
+
       // Store all the item sizes into the cache in advance, to prevent
       // interleave measuring with mutating dom.
       if (!this.fixedHeight_)
         this.ensureAllItemSizesInCache();
 
       // We cache the list items since creating the DOM nodes is the most
       // expensive part of redrawing.
       var cachedItems = this.cachedItems_ || {};
       var newCachedItems = {};
 
       var autoExpands = this.autoExpands_;
-      var scrollTop = this.scrollTop;
-      var clientHeight = this.clientHeight;
 
       var itemsInViewPort = this.getItemsInViewPort(scrollTop, clientHeight);
       // Draws the hidden rows just above/below the viewport to prevent
       // flashing in scroll.
       var firstIndex = Math.max(0, itemsInViewPort.first - 1);
       var lastIndex = Math.min(itemsInViewPort.last + 1, dataModel.length);
 
       var beforeFillerHeight =
           this.autoExpands ? 0 : this.getItemTop(firstIndex);
       var afterFillerHeight =
@@ skipping 100 matching lines @@
    * because list items can contain controls that can be focused, and for some
    * purposes (e.g., styling), the list can still be conceptually focused at
    * that point even though it doesn't actually have the page focus.
    */
   cr.defineProperty(List, 'hasElementFocus', cr.PropertyKind.BOOL_ATTR);
 
   return {
     List: List
   }
 });