Oilpan: Build fix after r170314

r170314 broke oilpan's build. This CL fixes it.

TBR=ager

Review URL: https://codereview.chromium.org/216433005

git-svn-id: svn://svn.chromium.org/blink/trunk@170319 bbb929c8-8fbe-4397-9dbb-9b2b20218538