[giow] (1) Kill History objects on non-active docs
Fixing https://www.w3.org/Bugs/Public/show_bug.cgi?id=23359
Affected topics: DOM APIs, Offline Web Applications, Security

git-svn-id: http://svn.whatwg.org/webapps@8302 340c8d12-0b0e-0410-8428-c7bf67bfef74