Fix the build from revert in r159372

EventNames -> EventTypeNames apparently.

TBR=ojan@chromium.org
BUG=306179

Review URL: https://codereview.chromium.org/26915002

git-svn-id: svn://svn.chromium.org/blink/trunk@159373 bbb929c8-8fbe-4397-9dbb-9b2b20218538