[FileBrowser] Added DefaultAction dialog to choose default action.

chrome/browser/resources/file_manager/js/combobutton.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.
 
 /**
  * @fileoverview This implements a combobutton control.
  */
 
 cr.define('cr.ui', function() {
   /**
@@ skipping 17 matching lines @@
       this.menu.clear();
       this.multiple = false;
     },
 
     addDropDownItem: function(item) {
       this.multiple = true;
       this.menu.addMenuItem(item).data = item;
     },
 
     /**
+     * Adds separator to drop-down list.
+     */
+    addSeparator: function() {
+      this.menu.addSeparator();
+    },
+
+    /**
      * Default item to fire on combobox click
      */
     get defaultItem() {
       return this.defaultItem_;
     },
     set defaultItem(defaultItem) {
       this.defaultItem_ = defaultItem;
       if (defaultItem.label) {
         this.labelNode_.textContent = defaultItem.label;
       } else {
@@ skipping 79 matching lines @@
     }
   };
 
   cr.defineProperty(ComboButton, 'disabled', cr.PropertyKind.BOOL_ATTR);
   cr.defineProperty(ComboButton, 'multiple', cr.PropertyKind.BOOL_ATTR);
 
   return {
     ComboButton: ComboButton
   };
 });