Introduce ComposedTreeTraversal::previousPostOrder()

Source/core/dom/shadow/ComposedTreeTraversal.h

 /*
  * Copyright (C) 2012 Google 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:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Neither the name of Google Inc. nor the names of its
@@ skipping 64 matching lines @@
     // Composed tree version of |NodeTraversal::nextSkippingChildren()|. This
     // function is similar to |next()| but skips child nodes of a specified
     // node.
     static Node* nextSkippingChildren(const Node&);
     static Node* nextSkippingChildren(const Node&, const Node* stayWithin);
 
     // Composed tree version of |NodeTraversal::previousSkippingChildren()|
     // similar to |previous()| but skipping child nodes of the specified node.
     static Node* previousSkippingChildren(const Node&);
 
+    // Like previous, but visits parents before their children.
+    static Node* previousPostOrder(const Node&, const Node* stayWithin = nullptr);
+
     // Composed tree version of |Node::isDescendantOf(other)|. This function
     // returns true if |other| contains |node|, otherwise returns
     // false. If |other| is |node|, this function returns false.
     static bool isDescendantOf(const Node& /*node*/, const Node& other);
 
     static bool contains(const ContainerNode& container, const Node& node)
     {
         assertPrecondition(container);
         assertPrecondition(node);
         return container == node || isDescendantOf(node, container);
@@ skipping 208 matching lines @@
 }
 
 inline Node* ComposedTreeTraversal::traverseLastChild(const Node& node)
 {
     return traverseChild(node, TraversalDirectionBackward);
 }
 
 } // namespace
 
 #endif