Oilpan: fix build after r174194.

Fix compilation errors (unused variable warnings-as-errors) in
AnimationTest.cpp

R=
BUG=340522
NOTRY=true

Review URL: https://codereview.chromium.org/293473003

git-svn-id: svn://svn.chromium.org/blink/trunk@174234 bbb929c8-8fbe-4397-9dbb-9b2b20218538