diff -r 000000000000 -r 6474c204b198 content/base/src/TreeWalker.h
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/content/base/src/TreeWalker.h	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,110 @@
+/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
+/* vim: set ts=4 et sw=4 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+ 
+/*
+ * Implementation of DOM Traversal's nsIDOMTreeWalker
+ */
+
+#ifndef mozilla_dom_TreeWalker_h
+#define mozilla_dom_TreeWalker_h
+
+#include "nsIDOMTreeWalker.h"
+#include "nsTraversal.h"
+#include "nsCOMPtr.h"
+#include "nsTArray.h"
+#include "nsCycleCollectionParticipant.h"
+
+class nsINode;
+class nsIDOMNode;
+
+namespace mozilla {
+namespace dom {
+
+class TreeWalker MOZ_FINAL : public nsIDOMTreeWalker, public nsTraversal
+{
+public:
+    NS_DECL_CYCLE_COLLECTING_ISUPPORTS
+    NS_DECL_NSIDOMTREEWALKER
+
+    TreeWalker(nsINode *aRoot,
+               uint32_t aWhatToShow,
+               const NodeFilterHolder &aFilter);
+    virtual ~TreeWalker();
+
+    NS_DECL_CYCLE_COLLECTION_CLASS(TreeWalker)
+
+    // WebIDL API
+    nsINode* Root() const
+    {
+        return mRoot;
+    }
+    uint32_t WhatToShow() const
+    {
+        return mWhatToShow;
+    }
+    already_AddRefed<NodeFilter> GetFilter()
+    {
+        return mFilter.ToWebIDLCallback();
+    }
+    nsINode* CurrentNode() const
+    {
+        return mCurrentNode;
+    }
+    void SetCurrentNode(nsINode& aNode, ErrorResult& aResult);
+    // All our traversal methods return strong refs because filtering can
+    // remove nodes from the tree.
+    already_AddRefed<nsINode> ParentNode(ErrorResult& aResult);
+    already_AddRefed<nsINode> FirstChild(ErrorResult& aResult);
+    already_AddRefed<nsINode> LastChild(ErrorResult& aResult);
+    already_AddRefed<nsINode> PreviousSibling(ErrorResult& aResult);
+    already_AddRefed<nsINode> NextSibling(ErrorResult& aResult);
+    already_AddRefed<nsINode> PreviousNode(ErrorResult& aResult);
+    already_AddRefed<nsINode> NextNode(ErrorResult& aResult);
+
+    JSObject* WrapObject(JSContext *cx);
+
+private:
+    nsCOMPtr<nsINode> mCurrentNode;
+
+    /*
+     * Implements FirstChild and LastChild which only vary in which direction
+     * they search.
+     * @param aReversed Controls whether we search forwards or backwards
+     * @param aResult   Whether we threw or not.
+     * @returns         The desired node. Null if no child is found
+     */
+    already_AddRefed<nsINode> FirstChildInternal(bool aReversed,
+                                                 ErrorResult& aResult);
+
+    /*
+     * Implements NextSibling and PreviousSibling which only vary in which
+     * direction they search.
+     * @param aReversed Controls whether we search forwards or backwards
+     * @param aResult   Whether we threw or not.
+     * @returns         The desired node. Null if no child is found
+     */
+    already_AddRefed<nsINode> NextSiblingInternal(bool aReversed,
+                                                  ErrorResult& aResult);
+
+    // Implementation for our various XPCOM getters
+    typedef already_AddRefed<nsINode> (TreeWalker::*NodeGetter)(ErrorResult&);
+    inline nsresult ImplNodeGetter(NodeGetter aGetter, nsIDOMNode** aRetval)
+    {
+        mozilla::ErrorResult rv;
+        nsCOMPtr<nsINode> node = (this->*aGetter)(rv);
+        if (rv.Failed()) {
+            return rv.ErrorCode();
+        }
+        *aRetval = node ? node.forget().take()->AsDOMNode() : nullptr;
+        return NS_OK;
+    }
+};
+
+} // namespace dom
+} // namespace mozilla
+
+#endif // mozilla_dom_TreeWalker_h
+