Fix touch hit rect position for table cells

Fix touch hit rect position for table cells

RenderTableCell is unusual in that its location offset includes the offset of
its parent row.  We compensate for this in other places (like offsetFromContainer),
and so this CL also compensates for this in touch hit rect generation.

BUG=300283
Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=159498

[Rick Byers, 2013-10-11 02:29:22]

Levi,
Please review this little touch hit rect fix.  Before and after screenshots of
the main test case results are attached to the bug.

Thanks,
   Rick

[leviw_travelin_and_unemployed, 2013-10-11 20:58:34]

lgtm

[commit-bot: I haz the power, 2013-10-11 20:58:51]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/rbyers@chromium.org/26964002/1

[commit-bot: I haz the power, 2013-10-12 05:08:58]

Change committed as 159498