te-time increments.
       * Bind this to the `<input is="iron-input">`'s `step` property.
       */
      step: {
        type: String
      },

      /**
       * Bind this to the `<input is="iron-input">`'s `name` property.
       */
      name: {
        type: String
      },

      /**
       * A placeholder string in addition to the label. If this is set, the label will always float.
       */
      placeholder: {
        type: String,
        // need to set a default so _computeAlwaysFloatLabel is ru