Bug 847508 - Allow mach_bootstrap to specify a separate mozilla dir, for comm-central builds [r=gps]

DONTBUILD (not part of the build)
Merge m-c to inbound.
Bug 846971 - Don't create layers that are scaled to 0. r=roc
Bug 839029 - Don't repaint default button if disabled or inactive. r=mstange, r=josh
Bug 844774 - Move old samples to last one. r=khuey
Bug 845807 - Blue link text should be lighter by default. r=mconley, ui-r=shorlander
Bug 848664 - New intrinsics for self-hosted JavaScript missing from jshint globals. r=nmatsakis
Bug 848423 - Change nearly all WebRTC instances of linked_ptr<> to nsRefPtr<> r=ehugg
Bug 587251 - new Worker(badURL) should throw a SECURITY_ERR. r=khuey