Bug 884934 - Fix intermittent SM(r) failure on InitialShapeTable::Ptr; r=sfink

In EmptyShape::getInitialShape, the InitialShapeSet::AddPtr is not guarded and
will get poisoned by the analysis if the hash happens to look like a GC thing
pointer.

--HG--
extra : rebase_source : a831c92b4f9aabe631f5bea3d9d6efb4375170a8
Bug 883789 - Use baseline fallback stubs to track double-overflow of BinaryArith and UnaryArith ops.  r=h4writer
Bug 883827.  Make Optional<NonNull<T>> and Optional<OwningNonNull<T>> nicer to use by having their const Value() method return a T&.  r=peterv
Bug 884401.  Remove the hasXPConnectImpls annotations for HTMLElement, Element, and Node in WebIDL bindings, since all those are gone.  r=peterv
Bug 883887.  Add an Unlink method to js::ExpandoAndGeneration.  r=peterv