Add yhirano@ to Source/modules/websockets/OWNERS

All requirements listed here are met, I think.
http://dev.chromium.org/developers/owners-files

BUG=none

Review URL: https://codereview.chromium.org/59903007

git-svn-id: svn://svn.chromium.org/blink/trunk@161520 bbb929c8-8fbe-4397-9dbb-9b2b20218538