DialogFragmentのタイトル領域をなくす (メモ)
DialogFragment で onCreateDialog をオーバーライド
  override fun onCreateDialog(savedInstanceState: Bundle?): Dialog {
    val layout = RelativeLayout(activity)
    layout.layoutParams = ViewGroup.LayoutParams(ViewGroup.LayoutParams.MATCH_PARENT, ViewGroup.LayoutParams.MATCH_PARENT)
    val dialog = Dialog(activity)
    dialog.requestWindowFeature(Window.FEATURE_NO_TITLE)
    dialog.setContentView(layout)
    dialog.window!!.setBackgroundDrawable(ColorDrawable(Color.WHITE))
    dialog.window!!.setLayout(ViewGroup.LayoutParams.MATCH_PARENT, ViewGroup.LayoutParams.MATCH_PARENT)
    return dialog
  }