Add JSON test specs for master.chromium.win

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

Review URL: https://codereview.chromium.org/184873006

git-svn-id: http://src.chromium.org/chrome/trunk/src/testing@255230 4ff67af0-8c30-449e-8e8b-ad334ec8d88c
Updating Mac buildbots to run gcm_unit_tests

BUG=341513

Review URL: https://codereview.chromium.org/185943008

git-svn-id: http://src.chromium.org/chrome/trunk/src/testing@255302 4ff67af0-8c30-449e-8e8b-ad334ec8d88c