Add JSON test specs for recipe-enabled waterfalls

This will be used by https://codereview.chromium.org/179363008/

For an earlier similar change here please see https://codereview.chromium.org/166663004

BUG=338501, 332239
R=navabi@google.com

Review URL: https://codereview.chromium.org/182313003

git-svn-id: http://src.chromium.org/chrome/trunk/src/testing@253615 4ff67af0-8c30-449e-8e8b-ad334ec8d88c
Add gfx_unittests to linux / mac trybots.

BUG=331829

Review URL: https://codereview.chromium.org/178823004

git-svn-id: http://src.chromium.org/chrome/trunk/src/testing@253813 4ff67af0-8c30-449e-8e8b-ad334ec8d88c