[giow] (0) Allow addHitRegion() to refer to non-interactive table-related elements, so that we can expose grids in canvases (e.g. crosswords)
Fixing https://www.w3.org/Bugs/Public/show_bug.cgi?id=24750
Affected topics: Canvas

git-svn-id: http://svn.whatwg.org/webapps@8494 340c8d12-0b0e-0410-8428-c7bf67bfef74