diff -r 000000000000 -r 6474c204b198 dom/smil/nsSMILNullType.h
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/dom/smil/nsSMILNullType.h	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,49 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* 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 NS_SMILNULLTYPE_H_
+#define NS_SMILNULLTYPE_H_
+
+#include "mozilla/Attributes.h"
+#include "nsISMILType.h"
+
+class nsSMILNullType : public nsISMILType
+{
+public:
+  // Singleton for nsSMILValue objects to hold onto.
+  static nsSMILNullType*
+  Singleton()
+  {
+    static nsSMILNullType sSingleton;
+    return &sSingleton;
+  }
+
+protected:
+  // nsISMILType Methods
+  // -------------------
+  virtual void Init(nsSMILValue& aValue) const MOZ_OVERRIDE {}
+  virtual void Destroy(nsSMILValue& aValue) const MOZ_OVERRIDE {}
+  virtual nsresult Assign(nsSMILValue& aDest, const nsSMILValue& aSrc) const MOZ_OVERRIDE;
+
+  // The remaining methods should never be called, so although they're very
+  // simple they don't need to be inline.
+  virtual bool     IsEqual(const nsSMILValue& aLeft,
+                           const nsSMILValue& aRight) const MOZ_OVERRIDE;
+  virtual nsresult Add(nsSMILValue& aDest, const nsSMILValue& aValueToAdd,
+                       uint32_t aCount) const MOZ_OVERRIDE;
+  virtual nsresult ComputeDistance(const nsSMILValue& aFrom,
+                                   const nsSMILValue& aTo,
+                                   double& aDistance) const MOZ_OVERRIDE;
+  virtual nsresult Interpolate(const nsSMILValue& aStartVal,
+                               const nsSMILValue& aEndVal,
+                               double aUnitDistance,
+                               nsSMILValue& aResult) const MOZ_OVERRIDE;
+
+private:
+  // Private constructor: prevent instances beyond my singleton.
+  MOZ_CONSTEXPR nsSMILNullType() {}
+};
+
+#endif // NS_SMILNULLTYPE_H_