Table's columns and rows should not be modified outside.

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 42 matching lines @@
 
     virtual AccessibilityRole roleValue() const override final;
 
     virtual void addChildren() override;
     virtual void clearChildren() override final;
 
     // To be overridden by AXARIAGrid.
     virtual bool isAriaTable() const { return false; }
     virtual bool supportsSelectedRows() { return false; }
 
-    AccessibilityChildrenVector& columns();
-    AccessibilityChildrenVector& rows();
+    const AccessibilityChildrenVector& columns();
+    const AccessibilityChildrenVector& rows();
 
     unsigned columnCount();
     unsigned rowCount();
 
     virtual String title() const override final;
 
     // all the cells in the table
     void cells(AccessibilityChildrenVector&);
     AXTableCell* cellForColumnAndRow(unsigned column, unsigned row);
 
@@ skipping 13 matching lines @@
     bool hasARIARole() const;
     virtual bool isTableExposableThroughAccessibility() const;
     virtual bool computeAccessibilityIsIgnored() const override final;
 };
 
 DEFINE_AX_OBJECT_TYPE_CASTS(AXTable, isAXTable());
 
 } // namespace blink
 
 #endif // AXTable_h