MD User Manager: Hides 'import supervised user' link while loading supervised users.

chrome/browser/resources/md_user_manager/create_profile.html

 <link rel="import" href="/import_supervised_user.html">
 <link rel="import" href="/profile_browser_proxy.html">
 <link rel="import" href="/shared_styles.html">
 <link rel="import" href="chrome://resources/cr_elements/cr_profile_avatar_selector/cr_profile_avatar_selector.html">
 <link rel="import" href="chrome://resources/cr_elements/icons.html">
 <link rel="import" href="chrome://resources/html/action_link.html">
 <link rel="import" href="chrome://resources/html/cr.html">
 <link rel="import" href="chrome://resources/html/i18n_behavior.html">
 <link rel="import" href="chrome://resources/html/polymer.html">
 <link rel="import" href="chrome://resources/html/util.html">
@@ skipping 166 matching lines @@
                   attr-for-selected="data-user-index">
                 <template is="dom-repeat" items="[[signedInUsers_]]">
                   <paper-item data-user-index$="[[index]]">
                     [[item.username]]
                   </paper-item>
                 </template>
               </paper-listbox>
             </paper-dropdown-menu>
             <a id="import-user" is="action-link" on-tap="onImportUserTap_"
                 hidden="[[isImportUserLinkHidden_(createInProgress_,
+                                                  loadingSupervisedUsers_,
                                                   signedInUserIndex_)]]">
               $i18n{importExistingSupervisedUserLink}
             </a>
           </template>
           <div id="sign-in-howto-message"
               hidden="[[isSignedIn_(signedInUsers_)]]"
               inner-h-t-m-l="[[i18nAllowIDAttr_('noSignedInUserMessage')]]">
           </div>
         </template>
       </div>
@@ skipping 10 matching lines @@
                                         loadingSupervisedUsers_,
                                         profileName_)]]">
           $i18n{createProfileConfirm}
         </paper-button>
       </div>
       <import-supervised-user id="importUserPopup"></import-supervised-user>
     </div>
   </template>
   <script src="create_profile.js"></script>
 </dom-module>