Bug 1036214 - Do a subsumes check on object and any parameters (and things containing them) to JS-implemented WebIDL. r=bz, a=sledru
Bug 1036214 - Tests. r=bz, a=sledru

This whole test setup comes from bug 923904, so some of the things it's testing
need to be rejiggered (like the checkGlobal stuff).
Bug 1056468 - Clear metadata when history entries are removed. r=lucasr, a=sledru