reloadAndSaveState_() {
    const wasOpenArray = this.sections_.map((section) => section.getIsOpen());
    this.reload_();
    for (let i = 0; i < wasOpenArray.length; i++) {
      const wasOpen = wasOpenArray[i];
      const section = this.sections_[i];
      if (wasOpen) {
        section.open();
      }
    }

    // Update the componentHandler, to account for any new MDL elements added.
    componentHandler.upgradeDom();
  }
Remake the contents of the div. Unlike |reload_|, this will also remember
which sections were open.
@private