Oilpan: Fix build now that AnimationEffect is exposed to JavaScript.

TBR=haraken@chromium.org
NOTRY=true

Review URL: https://codereview.chromium.org/260083009

git-svn-id: svn://svn.chromium.org/blink/trunk@172851 bbb929c8-8fbe-4397-9dbb-9b2b20218538