Backout bug 829035 (9da8f50d3750) because of bug 829335

The pixman update is no good and this depends on it.
CLOSED TREE
Backout bug 828789 (bb755890ec69) because of bug 829335

Backout pixman update.
CLOSED TREE
Bug 829121 - Annotate B2G_OS_Version for the crash reporter. r=fabrice

--HG--
extra : rebase_source : 30d533413d9fa022bb30c504632a0fed340b9322
Bug 827490 - Allow native objects to have both slots and dense elements, rm dense/slow array distinction, r=billm, dvander.