onResizableBehavior,
        Polymer.IronSelectableBehavior
      ],

      properties: {

        // as the selected page is the only one visible, activateEvent
        // is both non-sensical and problematic; e.g. in cases where a user
        // handler attempts to change the page and the activateEvent
        // handler immediately changes it back
        activateEvent: {
          type: String,
          value: null
        }

      },

      observers: [
        '_selectedPageChanged(selected)'
      