Bug 899881 - Don't allow frames to have a null style context. r=dbaron
Bug 899886 - Don't return null from nsStyleSet::ReparentStyleContext. r=dbaron
Bug 899894 - Don't null check nsStyleSet::ResolveBlah return values. r=dbaron
Bug 899896 - Avoid null checking of some box layout factory functions. r=dbaron
Bug 899900 - Avoid null checking result of NS_NewBlahFrame. r=dbaron