Revert "Gardening. Mark compositing/lots-of-img-layers* Slow to see if they pass."
Revert "Gardening. Mark compositing/lots-of-img-layers* Slow to see if they pass."

Tests still timed out, even when marked as Slow.

git-svn-id: bf5cd6ccde378db821296732a091cfbcf5285fbd@152579 bbb929c8-8fbe-4397-9dbb-9b2b20218538

axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk