Bug=v8:6083
Test=intl/general/case-mapping.js

Change-Id: I254c54520262298d6843948654d1dc4583b0c245
Reviewed-on: https://chromium-review.googlesource.com/496886Reviewed-by: Adam Klein <adamk@chromium.org>
Commit-Queue: Jungshik Shin <jshin@chromium.org>
Cr-Commit-Position: refs/heads/master@{#45115}