Mentioned by ICU guru during design review. Bug in theory, but
cannot find a locale has 'b' and 'B' in the 12 date/time style
canned pattern.

Bug: v8:8877
Change-Id: I126fdf979e8ea5b97773c8fd974359a7e52f18e9
Reviewed-on: https://chromium-review.googlesource.com/c/1480922Reviewed-by: Frank Tang <ftang@chromium.org>
Reviewed-by: Sathya Gunasekaran <gsathya@chromium.org>
Commit-Queue: Frank Tang <ftang@chromium.org>
Cr-Commit-Position: refs/heads/master@{#59928}