Suppress tests that need to be rebaselined after http://crrev.com/26133002 lands

This suppresses ImageOnlyFailures for effect-reference-hidpi-hw.html and
effect-reference-zoom-hw.html, which will need to be rebaselined after
Chromium CL http://crrev.com/26133002 lands.

TBR=senorblanco@chromium.org
BUG=181613

Review URL: https://codereview.chromium.org/26546002

git-svn-id: svn://svn.chromium.org/blink/trunk@159145 bbb929c8-8fbe-4397-9dbb-9b2b20218538