Expose internal treegrid role, do some cleanup for table/grid/treegrid handling

third_party/WebKit/Source/modules/accessibility/AXARIAGrid.h

 /*
  * Copyright (C) 2009 Apple Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  *
  * 1.  Redistributions of source code must retain the above copyright
  *     notice, this list of conditions and the following disclaimer.
  * 2.  Redistributions in binary form must reproduce the above copyright
@@ skipping 30 matching lines @@
 
  private:
   AXARIAGrid(LayoutObject*, AXObjectCacheImpl&);
 
  public:
   static AXARIAGrid* Create(LayoutObject*, AXObjectCacheImpl&);
   ~AXARIAGrid() override;
 
   bool IsAriaTable() const override { return true; }
 
+  AccessibilityRole RoleValue() const final {
+    return AXLayoutObject::RoleValue();
+  }  // Use ARIA role
+
   void AddChildren() override;
 
  private:
   // ARIA treegrids and grids support selected rows.
   bool SupportsSelectedRows() override { return true; }
   bool IsMultiSelectable() const override { return true; }
   bool IsTableExposableThroughAccessibility() const override { return true; }
 
   bool AddTableRowChild(AXObject*,
                         HeapHashSet<Member<AXObject>>& appended_rows,
                         unsigned& column_count);
 };
 
 }  // namespace blink
 
 #endif  // AXARIAGrid_h