code: function (event) {
          var target = this || _global;
          var tasks = target[zoneSymbolEventNames[event.type][FALSE_STR]];
          if (tasks) {
              // invoke all tasks which attached to current target with given event.type and capture = false
              // for performance concern, if task.length === 1, just invoke
              if (tasks.length === 1) {
                  invokeTask(tasks[0], target, event);
              }
              else {
                  // https://github.com/angular/zone.js/issues/836
                  // copy the tasks array before invoke, to avoid
                  // the callback will remove itself or other listener
                  var copyTasks = tasks.slice();
                  for (var i = 0; i < copyTasks.length; i++) {
                      invokeTask(copyTasks[i], target, event);
                  }
              }
          }
      }
docs: global shared zoneAwareCallback to handle all event callback with capture = false