Avoid unnecessary copies of AccessibilityChildrenVector

Source/modules/accessibility/AXTableColumn.cpp

 /*
  * 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 61 matching lines @@
         return;
 
     LayoutObject* renderer = m_parent->renderer();
     if (!renderer)
         return;
 
     if (!m_parent->isAXTable())
         return;
 
     if (toAXTable(m_parent)->isAriaTable()) {
-        AccessibilityChildrenVector columnChildren = children();
+        const AccessibilityChildrenVector& columnChildren = children();
         unsigned childrenCount = columnChildren.size();
         for (unsigned i = 0; i < childrenCount; i++) {
             AXObject* cell = columnChildren[i].get();
             if (cell->roleValue() == ColumnHeaderRole)
                 headers.append(cell);
         }
         return;
     }
 
     if (!renderer->isTable())
@@ skipping 58 matching lines @@
         // make sure the last one isn't the same as this one (rowspan cells)
         if (m_children.size() > 0 && m_children.last() == cell)
             continue;
 
         m_children.append(cell);
         m_columnRect.unite(cell->elementRect());
     }
 }
 
 } // namespace blink