AX: Tables with <colgroups> are not reporting table column headers
https://bugs.webkit.org/show_bug.cgi?id=137846

Reviewed by Mario Sanchez Prada.

Source/WebCore:

The code to search for header objects was getting stuck on anonymous RenderTableSections.
We also need to check more rows for headers, in case the first row or more is not visible or is empty.

Test: accessibility/table-column-headers-with-captions.html

* accessibility/AccessibilityTableColumn.cpp:
(WebCore::AccessibilityTableColumn::headerObject):
(WebCore::AccessibilityTableColumn::headerObjectForSection):

LayoutTests:

* accessibility/table-column-headers-with-captions-expected.txt: Added.
* accessibility/table-column-headers-with-captions.html: Added.


git-svn-id: http://svn.webkit.org/repository/webkit/trunk@174860 268f45cc-cd09-0410-ab3c-d52691b4dbfc