Bug 842561 - Assert that our inheritance chain is correct for WebIDL objects. r=peterv, a=lsblakk

We could drop the descriptor for Text if we changed nsIDocument::CreateTextNode
to return an already_AddRefed<Text>, but then we'd need more casting in
nsDocument.cpp for the XPCOM CreateTextNode.  Not sure which way is better,
really.
Bug 842687 - Use uint32 instead of bool for certain plug-in values. r=bsmedberg, a=bajaj
Bug 842687 - Test for uint32_t plug-in value. r=bsmedberg, a=bajaj