Gardening: Mark same-script-different-lang.html flaky, NeedsRebaseline compositing tests

BUG=422846, 407079
TBR=cbiesinger

Review URL: https://codereview.chromium.org/650803002

git-svn-id: svn://svn.chromium.org/blink/trunk@183585 bbb929c8-8fbe-4397-9dbb-9b2b20218538