We need this new API to resolve bug 406382 across platforms.

See
http://bugs.icu-project.org/trac/ticket/11358
http://bugs.icu-project.org/trac/changeset/37148

BUG=406382
TEST=None
R=mark@chromium.org
TBR=mark@chromium.org

Review URL: https://codereview.chromium.org/1062503003