Comment 10 for bug 1178618

@Colin, @Hsin-Yi
I have done a new patch that adds 100ms delay and checks hotkey in:
file: ${src}/grub-core/normal/menu.c
...
  /* If timeout is 0, drawing is pointless (and ugly). */
  if (grub_menu_get_timeout () == 0)
    {
      *auto_boot = 1;
      return default_entry;
    }
...
With this patch, we only have to set --hotkey f9 to menuentry, and users can
press f9 to enter recovery mode even grub runs in quiet mode.