
  },

  /**
   * |selection| can be anything except a function, or else a function that
   * can return anything.
   *
   * In the context of trace_viewer, |selection| is typically an EventSet,
   * whose events will be highlighted by trace_viewer when this link is
   * clicked or mouse-entered.
   *
   * If |selection| is not a function, then it will be dispatched to this
   * link's embedder via a RequestSelectionChangeEvent when this link is
   * clicked or mouse-entered.
   *
   * If |selection| is a f