diff -r 000000000000 -r 6474c204b198 content/base/src/nsAtomListUtils.cpp
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/content/base/src/nsAtomListUtils.cpp	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,25 @@
+/* -*- 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/. */
+
+/*
+ * Static helper class for implementing atom lists.
+ */
+
+#include "nsAtomListUtils.h"
+#include "nsIAtom.h"
+#include "nsStaticAtom.h"
+
+/* static */ bool
+nsAtomListUtils::IsMember(nsIAtom *aAtom,
+                          const nsStaticAtom* aInfo,
+                          uint32_t aInfoCount)
+{
+    for (const nsStaticAtom *info = aInfo, *info_end = aInfo + aInfoCount;
+         info != info_end; ++info) {
+        if (aAtom == *(info->mAtom))
+            return true;
+    }
+    return false;
+}