diff -r 000000000000 -r 6474c204b198 layout/build/nsLayoutStatics.h
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/layout/build/nsLayoutStatics.h	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,71 @@
+/* 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/. */
+
+#ifndef nsLayoutStatics_h__
+#define nsLayoutStatics_h__
+
+#include "nscore.h"
+#include "MainThreadUtils.h"
+#include "nsISupportsImpl.h"
+#include "nsDebug.h"
+
+// This isn't really a class, it's a namespace for static methods.
+// Documents and other objects can hold a reference to the layout static
+// objects so that they last past the xpcom-shutdown notification.
+
+class nsLayoutStatics
+{
+public:
+  // Called by the layout module constructor. This call performs an AddRef()
+  // internally.
+  static nsresult Initialize();
+
+  static void AddRef()
+  {
+    NS_ASSERTION(NS_IsMainThread(),
+                 "nsLayoutStatics reference counting must be on main thread");
+
+    NS_ASSERTION(sLayoutStaticRefcnt,
+                 "nsLayoutStatics already dropped to zero!");
+
+    ++sLayoutStaticRefcnt;
+    NS_LOG_ADDREF(&sLayoutStaticRefcnt, sLayoutStaticRefcnt,
+                  "nsLayoutStatics", 1);
+  }
+  static void Release()
+  {
+    NS_ASSERTION(NS_IsMainThread(),
+                 "nsLayoutStatics reference counting must be on main thread");
+
+    --sLayoutStaticRefcnt;
+    NS_LOG_RELEASE(&sLayoutStaticRefcnt, sLayoutStaticRefcnt,
+                   "nsLayoutStatics");
+
+    if (!sLayoutStaticRefcnt)
+      Shutdown();
+  }
+
+private:
+  // not to be called!
+  nsLayoutStatics();
+
+  static void Shutdown();
+
+  static nsrefcnt sLayoutStaticRefcnt;
+};
+
+class nsLayoutStaticsRef
+{
+public:
+  nsLayoutStaticsRef()
+  {
+    nsLayoutStatics::AddRef();
+  }
+  ~nsLayoutStaticsRef()
+  {
+    nsLayoutStatics::Release();
+  }
+};
+
+#endif // nsLayoutStatics_h__