Take care not to destroy a multi-selection when a child element of a list item receives focus.

chrome/browser/resources/options/deletable_item_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.
 
 cr.define('options', function() {
   /** @const */ var List = cr.ui.List;
   /** @const */ var ListItem = cr.ui.ListItem;
 
   /**
    * Creates a deletable list item, which has a button that will trigger a call
@@ skipping 73 matching lines @@
     set deletable(value) {
       this.deletable_ = value;
       this.closeButtonElement_.disabled = !value;
     },
 
     /**
      * Called when a focusable child element receives focus. Selects this item
      * in the list selection model.
      * @private
      */
     handleFocus_: function() {

[Dan Beam, 2014/07/30 19:05:34]

if (this.selected)
  return;

[engedy, 2014/07/31 09:35:48]

Done.

       var list = this.parentNode;
       var index = list.getIndexOfListItem(this);
-      list.selectionModel.selectedIndex = index;
-      list.selectionModel.anchorIndex = index;
+
+      // This handler is also fired when the child receives focus as a result of
+      // the item getting selected by the customized mouse/keyboard handling in
+      // SelectionController. Take care not to destroy a potential multiple
+      // selection in this case.
+      if (!this.selected) {
+        list.selectionModel.selectedIndex = index;
+        list.selectionModel.anchorIndex = index;
+      }
     },
 
     /**
      * Don't let the list have a crack at the event. We don't want clicking the
      * close button to change the selection of the list or to focus on the close
      * button.
      * @param {Event} e The mouse down/up event object.
      * @private
      */
     handleMouseDownUpOnClose_: function(e) {
@@ skipping 80 matching lines @@
      */
     deleteItemAtIndex: function(index) {
     },
   };
 
   return {
     DeletableItemList: DeletableItemList,
     DeletableItem: DeletableItem,
   };
 });