animations/additive-transform-animations.html expectations after content shell.

BUG=242465
TBR=jochen@chromium.org

Review URL: https://codereview.chromium.org/15723003

git-svn-id: svn://svn.chromium.org/blink/trunk@150884 bbb929c8-8fbe-4397-9dbb-9b2b20218538