Oilpan: fix build after animation changes in r171024.

TBR=ager@chromium.org, shans@chromium.org
NOTRY=true
BUG=

Review URL: https://codereview.chromium.org/228113002

git-svn-id: svn://svn.chromium.org/blink/trunk@171028 bbb929c8-8fbe-4397-9dbb-9b2b20218538