Currently, there are a bunch of DOM fullscreen tests (as well as pointer lock tests) are disabled in various platforms because of their unreliability. After bug 1161802 and bug 1168028, the fullscreen behavior should be more reliable especially on Linux platform. And after bug 1105939, the behavior should be reliable on Mac platform. We should investigate those tests and try to enable them on the platforms they are disabled at present, once those bugs are fixed.

try push: https://treeherder.mozilla.org/#/jobs?repo=try&revision=74f209293d89 Everything looks fine... except a very high rate of bug 1174323 on OS X 10.10... I have disabled the specific subtest in that bug for OS X, so it should be fine now.