docs: function(event, opt_slice) {
        var thread = this.model_.getOrCreateProcess(event.pid).
            getOrCreateThread(event.tid);
        this.allFlowEvents_.push({
          refGuid: tr.b.GUID.getLastGuid(),
          sequenceNumber: this.allFlowEvents_.length,
          event: event,
          slice: opt_slice,  // slice for events that have flow info
          thread: thread
        });
      }