Mark tests that need to be rebaselined now that http://crrev.com/26133002 has landed

This marks effect-reference-hidpi-hw.html and effect-reference-zoom-hw.html
for rebaselining. These tests need to be rebaselined because of Chromium
CL http://crrev.com/26133002.

TBR=senorblanco@chromium.org
BUG=181613

Review URL: https://codereview.chromium.org/26843002

git-svn-id: svn://svn.chromium.org/blink/trunk@159334 bbb929c8-8fbe-4397-9dbb-9b2b20218538