Make HTMLCollection / NodeList backward traversal consistent with forward one

Source/core/dom/ElementTraversal.h

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  *           (C) 2001 Dirk Mueller (mueller@kde.org)
  * Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2011, 2012, 2013 Apple Inc. All rights reserved.
  * Copyright (C) 2008, 2009 Torch Mobile Inc. All rights reserved. (http://www.torchmobile.com/)
  * Copyright (C) 2014 Samsung Electronics. All rights reserved.
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
@@ skipping 27 matching lines @@
     static ElementType* firstChild(const ContainerNode& current) { return firstChildTemplate(current); }
     static ElementType* firstChild(const Node& current) { return firstChildTemplate(current); }
     static ElementType* lastChild(const ContainerNode& current) { return lastChildTemplate(current); }
     static ElementType* lastChild(const Node& current) { return lastChildTemplate(current); }
 
     // First ElementType ancestor of the node.
     static ElementType* firstAncestor(const Node& current);
     static ElementType* firstAncestorOrSelf(Node& current) { return firstAncestorOrSelfTemplate(current); }
     static ElementType* firstAncestorOrSelf(Element& current) { return firstAncestorOrSelfTemplate(current); }
 
     // First or last ElementType descendant of the node.

[Inactive, 2014/04/09 23:14:29]

BTW, the comment here clearly says we are supposed to return the last
*descendant* of the node. This is currently true for non-pure Elements. However,
for pure Elements, it was returning the last child of the node.

Also note that there is already an ElementTraversal::lastChild() to return the
last child Element of a Node.

I made this mistake when I refactored the ElementTraversal class because
ElementTraversal::firstWithin() *is* identical to
ElementTraversal::firstChild(). I (wrongly) did the same thing for
ElementTraversal::lastWithin() / ElementTraversal::lastChild().

     // For Elements firstWithin() is always the same as firstChild().
     static ElementType* firstWithin(const ContainerNode& current) { return firstWithinTemplate(current); }
     static ElementType* firstWithin(const Node& current) { return firstWithinTemplate(current); }
     static ElementType* lastWithin(const ContainerNode& current) { return lastWithinTemplate(current); }
     static ElementType* lastWithin(const Node& current) { return lastWithinTemplate(current); }
 
     // Pre-order traversal skipping non-element nodes.
     static ElementType* next(const ContainerNode& current) { return nextTemplate(current); }
     static ElementType* next(const Node& current) { return nextTemplate(current); }
     static ElementType* next(const ContainerNode& current, const Node* stayWithin) { return nextTemplate(current, stayWithin); }
@@ skipping 53 matching lines @@
 template <class NodeType>
 inline Element* Traversal<Element>::firstWithinTemplate(NodeType& current)
 {
     return firstChildTemplate(current);
 }
 
 template <>
 template <class NodeType>
 inline Element* Traversal<Element>::lastWithinTemplate(NodeType& current)
 {
-    return lastChildTemplate(current);
+    Node* node = NodeTraversal::lastWithin(current);

[Inactive, 2014/04/09 23:19:07]

Also see that WebKit is doing the same thing that I propose there:
http://trac.webkit.org/browser/trunk/Source/WebCore/dom/ElementTraversal.h#L107

+    while (node && !node->isElementNode())
+        node = NodeTraversal::previous(*node, &current);
+    return toElement(node);
 }
 
 template <>
 template <class NodeType>
 inline Element* Traversal<Element>::nextTemplate(NodeType& current)
 {
     Node* node = NodeTraversal::next(current);
     while (node && !node->isElementNode())
         node = NodeTraversal::nextSkippingChildren(*node);
     return toElement(node);
@@ skipping 198 matching lines @@
 {
     Node* node = current.nextSibling();
     while (node && !isElementOfType<const ElementType>(*node))
         node = node->nextSibling();
     return toElement<ElementType>(node);
 }
 
 } // namespace WebCore
 
 #endif