Revert 181758 "Simplify DOMWindowProperty and its unregistration."

This CL caused use-after-free in :LocalDOMWindow::willDetachDocumentFromFrame.
https://code.google.com/p/chromium/issues/detail?id=413316

> Simplify DOMWindowProperty and its unregistration.
> 
> As LocalDOMWindow controls the registration lifetime of its
> DOMWindowProperties, there's no need to offer a separate unregistration
> mechanism. Remove it, simplify notification code + retire now unused
> LocalDOMWindow back reference on DOMWindowProperty.
> 
> R=haraken,ager
> BUG=
> 
> Review URL: https://codereview.chromium.org/558213002

TBR=sigbjornf@opera.com

Review URL: https://codereview.chromium.org/564013002

git-svn-id: svn://svn.chromium.org/blink/trunk@181867 bbb929c8-8fbe-4397-9dbb-9b2b20218538