[giow] (2) Clarify that the collection's root might change during the collection's lifetime.
Fixing https://www.w3.org/Bugs/Public/show_bug.cgi?id=17195
Affected topics: Microdata

git-svn-id: http://svn.whatwg.org/webapps@7706 340c8d12-0b0e-0410-8428-c7bf67bfef74
[e] (0) Cleanup
Affected topics: DOM APIs, HTML, Microdata

git-svn-id: http://svn.whatwg.org/webapps@7707 340c8d12-0b0e-0410-8428-c7bf67bfef74