Make FindBuffer handle Japanese kana texts correctly

Previously FindBuffer doesn't do special handling of kana characters
like SearchBuffer did, resulting in incorect matching of characters that
aren't supposed to be matched, like ひand び.

Bug: 868227
Change-Id: Id9c7bb7fc38b9256ca6953057677204c0a7063bf
Reviewed-on: https://chromium-review.googlesource.com/c/1444896
Reviewed-by: Yoshifumi Inoue <yosin@chromium.org>
Commit-Queue: Rakina Zata Amni <rakina@chromium.org>
Cr-Commit-Position: refs/heads/master@{#627869}
5 files changed