Changes

'''Related bugs''': [https://bugzilla.mozilla.org/show_bug.cgi?id=1278356 Tracking bug], automatically started (no bug), [https://bugzilla.mozilla.org/show_bug.cgi?id=1272751 unblock GTK+ 3.20+], [https://bugzilla.mozilla.org/show_bug.cgi?id=1275040 block on OSX 10.6-10.8], [https://bugzilla.mozilla.org/show_bug.cgi?id=1275039 block on release WinXP], [https://bugzilla.mozilla.org/show_bug.cgi?id=1277882 block on linux a11y], [https://bugzilla.mozilla.org/show_bug.cgi?id=1237769 block on WinXP+Accel]