code: function indexOf(obj, element, index) {
        return obj.indexOf ? obj.indexOf(element, index) : _indexOf.call(obj, element, index);
      }
docs: Calls the indexOf function on the passed object with a specified callback. This
  uses `Ember.ArrayPolyfill`'s-indexOf method when necessary.
  
  @method indexOf
  @param {Object} obj The object to call indexOn on
  @param {Function} callback The callback to execute
  @param {Object} index The index to start searching from