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
--HG--
extra : rebase_source : f9dcc6b06e9ebf9c30a576f9319f76a51b6dc26f