need to access
   * properties or methods that are not exposed.
   * @polymerBehavior Polymer.PaperInputBehavior
   */
  Polymer.PaperInputBehaviorImpl = {

    properties: {
      /**
       * Fired when the input changes due to user interaction.
       *
       * @event change
       */

      /**
       * The label for this input. Bind this to `<paper-input-container>`'s `label` property.
       */
      label: {
        type: String
      },

      /**
       * The value for this input. Bind this to the