code: function preferencesGet(name) {
      return this.initializedPromise.then(function () {
        var defaultValue = DEFAULT_PREFERENCES[name];
  
        if (defaultValue === undefined) {
          throw new Error('preferencesGet: \'' + name + '\' is undefined.');
        } else {
          var prefValue = this.prefs[name];
  
          if (prefValue !== undefined) {
            return prefValue;
          }
        }
        return defaultValue;
      }.bind(this));
    }
docs: Get the value of a preference.
  @param {string} name The name of the preference whose value is requested.
  @return {Promise} A promise that is resolved with a {boolean|number|string}
  containing the value of the preference.