Oilpan: fix android build after r180901

TBR=keishi@chromium.org
NOTRY=true

Review URL: https://codereview.chromium.org/545133002

git-svn-id: svn://svn.chromium.org/blink/trunk@181453 bbb929c8-8fbe-4397-9dbb-9b2b20218538