Bug 1035164 - fix nullcheck in CustomizableWidgets, remove warning for items without shortcut in subviews, r=jaws

--HG--
extra : rebase_source : 0b58d1d43a877f8776ac99fe20dda9c4495c4643
Bug 1035211 - don't call acceptDialog for privacy pane private browsing change in in-content prefs, r=jaws

--HG--
extra : rebase_source : cde84a8a08de69f205b1572d85f270c28b6de56f