Use rowgroup and columgroup properties to expose table headers.

Source/modules/accessibility/AXTableCell.cpp

Index: Source/modules/accessibility/AXTableCell.cpp
diff --git a/Source/modules/accessibility/AXTableCell.cpp b/Source/modules/accessibility/AXTableCell.cpp
index 306215b4391ecc746a0e4d5c204d56c878902912..f5a678d957dbc1eec2d777e1ba441ddf8efa5c69 100644
--- a/Source/modules/accessibility/AXTableCell.cpp
+++ b/Source/modules/accessibility/AXTableCell.cpp
@@ -56,6 +56,18 @@ bool AXTableCell::isTableHeaderCell() const
     return node() && node()->hasTagName(thTag);
 }
 
+bool AXTableCell::isRowHeaderCell() const
+{
+    const AtomicString& scope = getAttribute(scopeAttr);
+    return equalIgnoringCase(scope, "row") || equalIgnoringCase(scope, "rowgroup");
+}
+
+bool AXTableCell::isColumnHeaderCell() const
+{
+    const AtomicString& scope = getAttribute(scopeAttr);
+    return equalIgnoringCase(scope, "col") || equalIgnoringCase(scope, "colgroup");
+}
+
 bool AXTableCell::computeAccessibilityIsIgnored() const
 {
     AXObjectInclusion decision = defaultObjectInclusion();
@@ -113,10 +125,10 @@ AccessibilityRole AXTableCell::scanToDecideHeaderRole()
         return CellRole;
 
     // Check scope attribute first.
-    const AtomicString& scope = getAttribute(scopeAttr);
-    if (equalIgnoringCase(scope, "row"))
+    if (isRowHeaderCell())
         return RowHeaderRole;
-    if (equalIgnoringCase(scope, "col"))
+
+    if (isColumnHeaderCell())
         return ColumnHeaderRole;
 
     // Check the previous cell and the next cell