Skip should-not-repaint-composited-descendants.html while we figure out why it's broken

BUG=365865
NOTRY=true
NOTREECHECKS=true

Review URL: https://codereview.chromium.org/247733003

git-svn-id: svn://svn.chromium.org/blink/trunk@172177 bbb929c8-8fbe-4397-9dbb-9b2b20218538