Fix regression in cutout-rects over NPAPI not working. This was caused by a typo in r157106.

BUG=302381

Review URL: https://codereview.chromium.org/26416003

git-svn-id: svn://svn.chromium.org/blink/trunk@159085 bbb929c8-8fbe-4397-9dbb-9b2b20218538