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

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

 /*
  * Copyright (C) 2008 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 36 matching lines @@
  public:
   static AXTable* Create(LayoutObject*, AXObjectCacheImpl&);
   ~AXTable() override;
   DECLARE_VIRTUAL_TRACE();
 
   void Init() final;
 
   bool IsAXTable() const final;
   bool IsDataTable() const final;
 
-  AccessibilityRole RoleValue() const final;
+  AccessibilityRole RoleValue() const;
 
   void AddChildren() override;
   void ClearChildren() final;
 
   // To be overridden by AXARIAGrid.
   virtual bool IsAriaTable() const { return false; }
   virtual bool SupportsSelectedRows() { return false; }
 
   const AXObjectVector& Columns();
   const AXObjectVector& Rows();
@@ skipping 21 matching lines @@
   bool HasARIARole() const;
   virtual bool IsTableExposableThroughAccessibility() const;
   bool ComputeAccessibilityIsIgnored(IgnoredReasons* = nullptr) const final;
 };
 
 DEFINE_AX_OBJECT_TYPE_CASTS(AXTable, IsAXTable());
 
 }  // namespace blink
 
 #endif  // AXTable_h