Bug 1068225 - Fix up assertion to check the right thing. r=bholley
Bug 1030420 - QI the pref service to the appropriate interface. r=billm

nsIPrefService and nsIPrefBranch are implemented by the same XPCOM object, but
getBranch lives on nsIPrefService rather than nsIPrefBranch. The bug here is
only noticeable if nobody has already QIed the per-scope-singleton object to
nsIPrefService. If we create two scopes where there previously was one, that's
more likely to be the case, and manifest itself as the bc1 orange we see on TBPL.
Bug 1030420 - Fix up unwrapDebuggerObjectGlobal to handle addon scopes. r=jimb
Bug 1030420 - Enable compartment-per-addon on Nightly. r=bholley