Blink gardening: set NeedsRebaseline for lots-of-img-layers tests.

These stopped crashing after r273650.

TBR=jbauman@chromium.org
NOTRY=true
BUG=None

Review URL: https://codereview.chromium.org/310463004

git-svn-id: svn://svn.chromium.org/blink/trunk@175144 bbb929c8-8fbe-4397-9dbb-9b2b20218538