diff -r 000000000000 -r 6474c204b198 dom/xslt/xpath/nsXPathNSResolver.cpp
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/dom/xslt/xpath/nsXPathNSResolver.cpp	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,46 @@
+/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
+/* 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/. */
+
+#include "nsXPathNSResolver.h"
+#include "nsDOMClassInfoID.h"
+#include "nsDOMString.h"
+
+NS_IMPL_CYCLE_COLLECTION(nsXPathNSResolver, mNode)
+
+NS_IMPL_CYCLE_COLLECTING_ADDREF(nsXPathNSResolver)
+NS_IMPL_CYCLE_COLLECTING_RELEASE(nsXPathNSResolver)
+
+DOMCI_DATA(XPathNSResolver, nsXPathNSResolver)
+
+NS_INTERFACE_MAP_BEGIN_CYCLE_COLLECTION(nsXPathNSResolver)
+  NS_INTERFACE_MAP_ENTRY(nsIDOMXPathNSResolver)
+  NS_INTERFACE_MAP_ENTRY_AMBIGUOUS(nsISupports, nsIDOMXPathNSResolver)
+  NS_DOM_INTERFACE_MAP_ENTRY_CLASSINFO(XPathNSResolver)
+NS_INTERFACE_MAP_END
+
+nsXPathNSResolver::nsXPathNSResolver(nsIDOMNode* aNode)
+  : mNode(aNode)
+{
+    NS_ASSERTION(mNode, "Need a node to resolve namespaces.");
+}
+
+NS_IMETHODIMP
+nsXPathNSResolver::LookupNamespaceURI(const nsAString & aPrefix,
+                                      nsAString & aResult)
+{
+    if (aPrefix.EqualsLiteral("xml")) {
+        aResult.AssignLiteral("http://www.w3.org/XML/1998/namespace");
+
+        return NS_OK;
+    }
+
+    if (!mNode) {
+        SetDOMStringToNull(aResult);
+
+        return NS_OK;
+    }
+
+    return mNode->LookupNamespaceURI(aPrefix, aResult);
+}