MD Settings: Bluetooth: Add error dialog and messages

ui/webui/resources/js/i18n_behavior.js

 // Copyright 2015 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
  * 'I18nBehavior' is a behavior to mix in loading of
  * internationalization strings.
  *
  * Example:
@@ skipping 39 matching lines @@
    * @param {{substitutions: (Array<string>|undefined),
    *          attrs: (Object<function(Node, string):boolean>|undefined),
    *          tags: (Array<string>|undefined)}} opts
    */
   i18nAdvanced: function(id, opts) {
     var args = [id].concat(opts.substitutions || []);
     var rawString = this.i18nRaw_.apply(this, args);
     return parseHtmlSubset('<b>' + rawString + '</b>', opts.tags, opts.attrs)
         .firstChild.innerHTML;
   },
+
+  /**
+   * Returns true if a translation exists for |id|.
+   * @param {string} id
+   * @return {boolean}
+   */
+  i18nExists: function(id) {
+    return loadTimeData.valueExists(id);
+  },
 };