Use rowgroup and columgroup properties to expose table headers.

Source/modules/accessibility/AXTableCell.h

Index: Source/modules/accessibility/AXTableCell.h
diff --git a/Source/modules/accessibility/AXTableCell.h b/Source/modules/accessibility/AXTableCell.h
index f8fdd6ec628ca48fee55c618cb501023735cea82..d0a36af71273cc1fdb0ff5f07836549439f66d5b 100644
--- a/Source/modules/accessibility/AXTableCell.h
+++ b/Source/modules/accessibility/AXTableCell.h
@@ -58,6 +58,9 @@ protected:
 
 private:
     bool isTableHeaderCell() const;
+    bool isRowHeaderCell() const;
+    bool isColumnHeaderCell() const;
+
     AccessibilityRole scanToDecideHeaderRole();
     // If a table cell is not exposed as a table cell, a TH element can serve as its title UI element.
     virtual AXObject* titleUIElement() const override final;