Add fast path for tag#id selector queries

Source/core/dom/TreeScope.h

 /*
  * Copyright (C) 2011 Google Inc. All Rights Reserved.
  * Copyright (C) 2012 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 39 matching lines @@
 class TreeScope {
     friend class Document;
     friend class TreeScopeAdopter;
 
 public:
     TreeScope* parentTreeScope() const { return m_parentTreeScope; }
     void setParentTreeScope(TreeScope*);
 
     Element* adjustedFocusedElement() const;
     Element* getElementById(const AtomicString&) const;
+    const Vector<Element*>& getAllElementsById(const AtomicString&) const;
     bool hasElementWithId(StringImpl* id) const;
     bool containsMultipleElementsWithId(const AtomicString& id) const;
     void addElementById(const AtomicString& elementId, Element*);
     void removeElementById(const AtomicString& elementId, Element*);
 
     Document* documentScope() const { return m_documentScope; }
 
     Node* ancestorInThisScope(Node*) const;
 
     void addImageMap(HTMLMapElement*);
@@ skipping 116 matching lines @@
 inline bool operator!=(const TreeScope& a, const TreeScope& b) { return !(a == b); }
 inline bool operator!=(const TreeScope& a, const TreeScope* b) { return !(a == b); }
 inline bool operator!=(const TreeScope* a, const TreeScope& b) { return !(a == b); }
 
 RenderObject* rendererFromPoint(Document*, int x, int y, LayoutPoint* localPoint = 0);
 TreeScope* commonTreeScope(Node*, Node*);
 
 } // namespace WebCore
 
 #endif // TreeScope_h