[giow] (3) Example window.opener cross-origin.
Fixing https://www.w3.org/Bugs/Public/show_bug.cgi?id=21970
Affected topics: DOM APIs, Security

git-svn-id: http://svn.whatwg.org/webapps@7941 340c8d12-0b0e-0410-8428-c7bf67bfef74

Author:    ianh <ianh@340c8d12-0b0e-0410-8428-c7bf67bfef74>