(Path is actually r=froydnj.)
Bug 1400459 devirtualized nsIAtom so that it is no longer a subclass of
nsISupports. This means that nsAtom is now a better name for it than nsIAtom.
MozReview-Commit-ID: 91U22X2NydP
Giving '0' (literal zero) to nsCOMPtr is now ambiguous, as both
nsCOMPtr(decltype(nullptr)) and nsCOMPtr(T*) could be used.
In any case, our coding standards mandate the use of 'nullptr' for pointers.
So I'm changing all zeroes into nullptr's where necessary.
MozReview-Commit-ID: LXiZTu87Ck6
