t to true to disable canceling the overlay by clicking outside it.
       */
      noCancelOnOutsideClick: {
        type: Boolean,
        value: false
      },

      /**
       * Contains the reason(s) this overlay was last closed (see `iron-overlay-closed`).
       * `IronOverlayBehavior` provides the `canceled` reason; implementers of the
       * behavior can provide other reasons in addition to `canceled`.
       */
      closingReason: {
        // was a getter before, but needs to be a property so 