Bug 872285 - bump packages and mirror to m-c for bug 790765;r=ahal

--HG--
rename : testing/mozbase/mozfile/tests/is_url.py => testing/mozbase/mozfile/tests/test_url.py
Bug 876074: Soften flexbox assertion about out-of-order children, since it's not dangerous and it can be triggered by unrelated-to-flexbox tree mutations. r=bz