Bug 830948, null check mDocshell before using it, r=bz

--HG--
extra : rebase_source : ea20dabe0ec39b3b98fab07e72b0f1f51f9d32a8
Bug 830893 - Remember private state for zombified tabs. r=mfinkle
Merge m-c to inbound.
Bug 817153 - AltiVec acceleration for qcms. r=jmuizelaar
Bug 829451 - Change the Firefox OS version to 1.0.0.0 (4 digits). r=fabrice
Bug 829832 - Move nss and sqlite builds before netwerk. r=mh