t is="iron-input">`'s
       * `required` property.
       */
      required: {
        type: Boolean,
        value: false
      },

      /**
       * The error message to display when the input is invalid. Bind this to the
       * `<paper-input-error>`'s content, if using.
       */
      errorMessage: {
        type: String
      },

      /**
       * Set to true to show a character counter.
       */
      charCounter: {
        type: Boolean,
        value: false
      },

      /**
       * Set to 