Allows efficient lookup, instead of doing per cell fetch + match.

Change-Id: I3cd0d26a8fc91ed38fd339229fc0e948fb849f5e
Reviewed-on: https://gerrit.libreoffice.org/5454Reviewed-by: Kohei Yoshida <kohei.yoshida@suse.de>
Tested-by: Kohei Yoshida <kohei.yoshida@suse.de>