Remove Context::Scope from visitDOMWrapper
visitDOMWrapper should not create a Context::Scope.
Alternately, it should visit wrappers of all worlds
(currently the binding layer is assuming that wrappers of all worlds
are kept alive if any of the wrappers is alive).
Also it is important to remove the Context::Scope because if DOM has a long reference chain
to be visited, the Context::Scopes created on the stack can overflow and cause crashes.