storageChange = ev => {
      if (!ev.newValue) return // This is a call from removeItem.
      if (ev.key === CLIPBOARD_ID + '_startup') {
        // Another tab asked for our sessionStorage.
        localStorage.removeItem(CLIPBOARD_ID + '_startup')
        this.flashStorage()
      } else if (ev.key === CLIPBOARD_ID) {
        // Another tab sent data.
        sessionStorage.setItem(CLIPBOARD_ID, ev.newValue)
      }
    }
Transfers sessionStorage from one tab to another.
@param {!Event} ev Storage event.
@returns {void}