Adding new tryserver.chromium.* json files to allow the 'chromium' recipe to run on the tryserver.

R=iannucci@chromium.org
BUG=395196

Review URL: https://codereview.chromium.org/413223003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@285751 0039d316-1c4b-4281-b951-d872f2087c98

testing/buildbot/tryserver.chromium.mac.json

+{
+}

testing/buildbot/tryserver.chromium.win.json

+{
+}