[cgiowt] (3) Clarify what the start tag of the context node is when parsing
Fixing https://www.w3.org/Bugs/Public/show_bug.cgi?id=26783
Affected topics: HTML Syntax and Parsing

git-svn-id: https://svn.whatwg.org/webapps@8805 340c8d12-0b0e-0410-8428-c7bf67bfef74