Avoid WTF::Vector::at() and operator[] in core/xml.

third_party/WebKit/Source/core/xml/XPathNodeSet.h

 /*
  * Copyright (C) 2007 Alexey Proskuryakov <ap@webkit.org>
  *
  * 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
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 25 matching lines @@
 
 class NodeSet final : public GarbageCollected<NodeSet> {
  public:
   static NodeSet* create() { return new NodeSet; }
   static NodeSet* create(const NodeSet&);
   DEFINE_INLINE_TRACE() { visitor->trace(m_nodes); }
 
   size_t size() const { return m_nodes.size(); }
   bool isEmpty() const { return !m_nodes.size(); }
   Node* operator[](unsigned i) const { return m_nodes.at(i).get(); }
+  HeapVector<Member<Node>>::iterator begin() { return m_nodes.begin(); }
+  HeapVector<Member<Node>>::iterator end() { return m_nodes.end(); }
+  HeapVector<Member<Node>>::const_iterator begin() const {
+    return m_nodes.begin();
+  }
+  HeapVector<Member<Node>>::const_iterator end() const { return m_nodes.end(); }
   void reserveCapacity(size_t newCapacity) {
     m_nodes.reserveCapacity(newCapacity);
   }
   void clear() { m_nodes.clear(); }
   void swap(NodeSet& other) {
     std::swap(m_isSorted, other.m_isSorted);
     std::swap(m_subtreesAreDisjoint, other.m_subtreesAreDisjoint);
     m_nodes.swap(other.m_nodes);
   }
 
@@ skipping 29 matching lines @@
 
   bool m_isSorted;
   bool m_subtreesAreDisjoint;
   HeapVector<Member<Node>> m_nodes;
 };
 
 }  // namespace XPath
 
 }  // namespace blink
 #endif  // XPathNodeSet_h