Avoid unnecessary copies of AccessibilityChildrenVector

Source/modules/accessibility/AXARIAGrid.cpp

 /*
  * 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 89 matching lines @@
     for (RefPtr<AXObject> child = firstChild(); child; child = child->nextSibling()) {
 
         if (!addTableCellChild(child.get(), appendedRows, columnCount)) {
 
             // in case the layout tree doesn't match the expected ARIA hierarchy, look at the children
             if (!child->hasChildren())
                 child->addChildren();
 
             // The children of this non-row will contain all non-ignored elements (recursing to find them).
             // This allows the table to dive arbitrarily deep to find the rows.
-            AccessibilityChildrenVector children = child->children();
+            const AccessibilityChildrenVector& children = child->children();
             size_t length = children.size();
             for (size_t i = 0; i < length; ++i)
                 addTableCellChild(children[i].get(), appendedRows, columnCount);
         }
     }
 
     // make the columns based on the number of columns in the first body
     for (unsigned i = 0; i < columnCount; ++i) {
         AXTableColumn* column = toAXTableColumn(axCache->getOrCreate(ColumnRole));
         column->setColumnIndex((int)i);
         column->setParent(this);
         m_columns.append(column);
         if (!column->accessibilityIsIgnored())
             m_children.append(column);
     }
 
     AXObject* headerContainerObject = headerContainer();
     if (headerContainerObject && !headerContainerObject->accessibilityIsIgnored())
         m_children.append(headerContainerObject);
 }
 
 } // namespace blink