This rolls:
https://chromium.googlesource.com/chromium/deps/icu/+log/450be73..b34251f

Bug: v8:6252
Change-Id: I496f35bad1717105c8e450ce045f3e9929574e0f
Reviewed-on: https://chromium-review.googlesource.com/475652Reviewed-by: Adam Klein <adamk@chromium.org>
Commit-Queue: Michael Achenbach <machenbach@chromium.org>
Cr-Commit-Position: refs/heads/master@{#44672}