Bug 842726.  Kill off GetterShim and the classinfo support for chrome-only stuff on Document now that we can do that via WebIDL.  r=peterv
Bug 842561.  Assert that our inheritance chain is correct for WebIDL objects.  r=peterv

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 629801 Implement HTML5 <time> element. r=smaug, peterv, hsivonen