Added guard to not set scrollTop if it hasn't changed. Surprisingly, this speeds up the list.redraw…

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 1102 matching lines @@
       var listItem = null;
       if (leadIndex != -1 && newCachedItems[leadIndex])
         newCachedItems[leadIndex].lead = true;
       for (var y = firstIndex; y < lastIndex; y++) {
         if (sm.getIndexSelected(y))
           newCachedItems[y].selected = true;
         else if (y != leadIndex)
           listItem = newCachedItems[y];
       }
 
-      this.scrollTop = scrollTop;
-
       this.firstIndex_ = firstIndex;
       this.lastIndex_ = lastIndex;
 
       this.remainingSpace_ = itemsInViewPort.last > dataModel.length;
       this.cachedItems_ = newCachedItems;
 
       // Mesurings must be placed after adding all the elements, to prevent
       // performance reducing.
       if (!this.fixedHeight_) {
         for (var y = firstIndex; y < lastIndex; y++)
@@ skipping 113 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
   }
 });