Oilpan: Build fix after r170768

r170768 broke oilpan builds. This CL fixes it.

TBR=ager@chromium.org

Review URL: https://codereview.chromium.org/223833002

git-svn-id: svn://svn.chromium.org/blink/trunk@170771 bbb929c8-8fbe-4397-9dbb-9b2b20218538