apply (handler) {
    super.apply(handler, () => {
      this.stack.forEach((stackItem) => {
        console.assert(stackItem, 'stack item should not be null')
        stackItem && stackItem.apply(handler)
      })
    })
  }
Runs "apply" on all subcommands.
@param {module:history.HistoryEventHandler} handler
@fires module:history~Command#event:history
@returns {void}