Oilpan: fix build after r182602

TBR=haraken
BUG=413257
NOTRY=true

Review URL: https://codereview.chromium.org/598153002

git-svn-id: svn://svn.chromium.org/blink/trunk@182628 bbb929c8-8fbe-4397-9dbb-9b2b20218538