Mark virtual/threaded/animations/3d/transform-perspective.html as timing out on debug

Mark the virtual/threaded/animations/3d/transform-perspective.html test
as timing out on all debug bots as per flakiness dashboard data.

BUG=248938
TBR=ajuma@chromium.org

Review URL: https://codereview.chromium.org/200123004

git-svn-id: svn://svn.chromium.org/blink/trunk@169862 bbb929c8-8fbe-4397-9dbb-9b2b20218538