[giow] (1) Share the ownerDocument of template contents amongst the templates of a document.
Fixing https://www.w3.org/Bugs/Public/show_bug.cgi?id=23795
Affected topics: DOM APIs, HTML

git-svn-id: http://svn.whatwg.org/webapps@8270 340c8d12-0b0e-0410-8428-c7bf67bfef74