code: function() {
                  var orders = this.options.runtimeOrder || Runtime.orders,
                      type = this.type,
                      i, len;
      
                  if ( !type ) {
                      orders = orders.split( /\s*,\s*/g );
      
                      for ( i = 0, len = orders.length; i < len; i++ ) {
                          if ( Runtime.hasRuntime( orders[ i ] ) ) {
                              this.type = type = orders[ i ];
                              break;
                          }
                      }
                  }
      
                  return type;
              }
docs: 预测Uploader将采用哪个`Runtime`
  @grammar predictRuntimeType() => String
  @method predictRuntimeType
  @for  Uploader