this);
    },

    _mixinBehavior: function(b) {
      Object.getOwnPropertyNames(b).forEach(function(n) {
        switch (n) {
          case 'registered':
          case 'properties':
          case 'observers':
          case 'listeners':
          case 'keyPresses':
          case 'hostAttributes':
          case 'created':
          case 'attached':
          case 'detached':
          case 'attributeChanged':
          case 'configure':
          case 'ready':
            break;
          default:
   