Fix buffer overflow in _canonicalize.

Upstream bug is http://bugs.icu-project.org/trac/ticket/8984

BUG=chromium:106441
Review URL: http://codereview.chromium.org/8822005

git-svn-id: http://src.chromium.org/svn/trunk/deps/third_party/icu46@113543 4ff67af0-8c30-449e-8e8b-ad334ec8d88c
3 files changed