           observer: '_openedChanged'
          },

          /**
           * The orientation against which to align the menu dropdown
           * horizontally relative to the dropdown trigger.
           */
          horizontalAlign: {
            type: String,
            value: 'left',
            reflectToAttribute: true
          },

          /**
           * The orientation against which to align the menu dropdown
           * vertically relative to the dropdown trigger.
           */
          ver