Mark compositing tests for rebaselining on Mac after TiledLayer change.

TBR=sky@chromium.org
NOTRY=true
BUG=417182

Review URL: https://codereview.chromium.org/598493004

git-svn-id: svn://svn.chromium.org/blink/trunk@182574 bbb929c8-8fbe-4397-9dbb-9b2b20218538