MD Settings: validate startup URLs

chrome/browser/resources/settings/on_startup_page/startup_urls_page.html

 <link rel="import" href="chrome://resources/html/polymer.html">
 <link rel="import" href="chrome://resources/html/util.html">
 <link rel="import" href="chrome://resources/html/web_ui_listener_behavior.html">
 <link rel="import" href="chrome://resources/polymer/v1_0/paper-input/paper-input.html">
 <link rel="import" href="chrome://md-settings/settings_dialog.html">
 <link rel="import" href="chrome://md-settings/settings_shared_css.html">
 <link rel="import" href="chrome://md-settings/on_startup_page/startup_urls_page_browser_proxy.html">
 
 <dom-module id="settings-startup-urls-page">
   <link rel="import" type="css" href="on_startup_shared.css">
@@ skipping 12 matching lines @@
           <div class="favicon-image"
               style="background-image: [[getIconSet_(item.url)]]">
           </div>
           <div class="middle">
             <div class="text-elide">[[item.title]]</div>
             <div class="text-elide secondary">[[item.url]]</div>
           </div>
           <iron-icon on-tap="onRemoveUrlTap_" icon="clear"></iron-icon>
         </div>
       </template>
-      <div class="list-item list-button" on-tap="onAddPageTap_"
+      <div class="list-item list-button" id="addPage" on-tap="onAddPageTap_"
           i18n-content="onStartupAddNewPage">
       </div>
       <div class="list-item list-button" on-tap="onUseCurrentPagesTap_"
           i18n-content="onStartupUseCurrent">
       </div>
     </div>
 
     <settings-dialog id="addUrlDialog">
       <div class="title" i18n-content="onStartupAddNewPage"></div>
       <div class="body">
-        <paper-input class="flex" always-float-label
+        <paper-input class="flex" always-float-label id="newUrl"
             i18n-values="label:onStartupSiteUrl" value="{{newUrl_}}">
         </paper-input>
       </div>
       <div class="button-container">
         <div class="action-buttons">
           <paper-button class="cancel-button" on-tap="onCancelTap_"
               id="cancel" i18n-content="cancel"></paper-button>
-          <paper-button class="action-button" on-tap="onAddTap_"
-              i18n-content="add" disabled="[[!isAddEnabled_(newUrl_)]]">
+          <paper-button id="add" class="action-button" on-tap="onAddTap_"
+              i18n-content="add" disabled="[[!isNewUrlValid_]]">
           </paper-button>
         </div>
       </div>
     </settings-dialog>
   </template>
   <script src="startup_urls_page.js"></script>
 </dom-module>