Gardening: Expand virtual/threaded/animations expectations on Linux.

The following tests are marked Pass Timeout on Mac:

animation-direction-reverse-fill-mode.html
animation-direction-reverse-fill-mode-hardware.html

After r156414/Chromium r218597 these are also flakily timing out on
Linux.

BUG=248938
TBR=ccameron@chromium.org

Review URL: https://codereview.chromium.org/22935017

git-svn-id: svn://svn.chromium.org/blink/trunk@156431 bbb929c8-8fbe-4397-9dbb-9b2b20218538