code: function AsyncSliceGroup(parentContainer, opt_name) {
      tr.model.EventContainer.call(this);
      this.parentContainer_ = parentContainer;
      this.slices = [];
      this.name_ = opt_name;
      this.viewSubGroups_ = undefined;
    }
docs: A group of AsyncSlices associated with a thread.
  @constructor
  @extends {tr.model.EventContainer}