--- a/content/smil/SMILBoolType.h
+++ b/content/smil/SMILBoolType.h
@@ -35,17 +35,15 @@ protected:
                                    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 & destructor: prevent instances beyond my singleton,
-  // and prevent others from deleting my singleton.
-  SMILBoolType()  {}
-  ~SMILBoolType() {}
+  // Private constructor: prevent instances beyond my singleton.
+  MOZ_CONSTEXPR SMILBoolType() {}
 };
 
 } // namespace mozilla
 
 #endif // MOZILLA_SMILBOOLTYPE_H_

--- a/content/smil/SMILEnumType.h
+++ b/content/smil/SMILEnumType.h
@@ -36,17 +36,15 @@ protected:
                                    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 & destructor: prevent instances beyond my singleton,
-  // and prevent others from deleting my singleton.
-  SMILEnumType()  {}
-  ~SMILEnumType() {}
+  // Private constructor: prevent instances beyond my singleton.
+  MOZ_CONSTEXPR SMILEnumType() {}
 };
 
 } // namespace mozilla
 
 #endif // MOZILLA_SMILENUMTYPE_H_

--- a/content/smil/SMILIntegerType.h
+++ b/content/smil/SMILIntegerType.h
@@ -32,14 +32,14 @@ public:
   static SMILIntegerType*
   Singleton()
   {
     static SMILIntegerType sSingleton;
     return &sSingleton;
   }
 
 private:
-  SMILIntegerType() {}
+  MOZ_CONSTEXPR SMILIntegerType() {}
 };
 
 } // namespace mozilla
 
 #endif // MOZILLA_SMILINTEGERTYPE_H_

--- a/content/smil/SMILStringType.h
+++ b/content/smil/SMILStringType.h
@@ -36,17 +36,15 @@ protected:
                                    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 & destructor: prevent instances beyond my singleton,
-  // and prevent others from deleting my singleton.
-  SMILStringType()  {}
-  ~SMILStringType() {}
+  // Private constructor: prevent instances beyond my singleton.
+  MOZ_CONSTEXPR SMILStringType() {}
 };
 
 } // namespace mozilla
 
 #endif // MOZILLA_SMILSTRINGTYPE_H_

--- a/content/smil/nsISMILType.h
+++ b/content/smil/nsISMILType.h
@@ -1,16 +1,17 @@
 /* -*- 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_ISMILTYPE_H_
 #define NS_ISMILTYPE_H_
 
+#include "mozilla/Attributes.h"
 #include "nscore.h"
 
 class nsSMILValue;
 
 //////////////////////////////////////////////////////////////////////////////
 // nsISMILType: Interface for defining the basic operations needed for animating
 // a particular kind of data (e.g. lengths, colors, transformation matrices).
 //
@@ -202,18 +203,11 @@ protected:
    *          available for storing the result.
    *
    * @pre aStartVal.mType == aEndVal.mType == aResult.mType == this
    */
   virtual nsresult Interpolate(const nsSMILValue& aStartVal,
                                const nsSMILValue& aEndVal,
                                double aUnitDistance,
                                nsSMILValue& aResult) const = 0;
-
-  /**
-   * Protected destructor, to ensure that no one accidentally deletes an
-   * instance of this class.
-   * (The only instances in existence should be singletons - one per subclass.)
-   */
-  ~nsISMILType() {}
 };
 
 #endif // NS_ISMILTYPE_H_

--- a/content/smil/nsSMILCSSValueType.h
+++ b/content/smil/nsSMILCSSValueType.h
@@ -93,15 +93,13 @@ public:
    *
    * @param       aValue   The nsSMILValue to be converted into a string.
    * @param [out] aString  The string to be populated with the given value.
    * @return               true on success, false on failure.
    */
   static bool ValueToString(const nsSMILValue& aValue, nsAString& aString);
 
 private:
-  // Private constructor & destructor: prevent instances beyond my singleton,
-  // and prevent others from deleting my singleton.
-  nsSMILCSSValueType()  {}
-  ~nsSMILCSSValueType() {}
+  // Private constructor: prevent instances beyond my singleton.
+  MOZ_CONSTEXPR nsSMILCSSValueType() {}
 };
 
 #endif // NS_SMILCSSVALUETYPE_H_

--- a/content/smil/nsSMILFloatType.h
+++ b/content/smil/nsSMILFloatType.h
@@ -34,15 +34,13 @@ protected:
                                    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 & destructor: prevent instances beyond my singleton,
-  // and prevent others from deleting my singleton.
-  nsSMILFloatType()  {}
-  ~nsSMILFloatType() {}
+  // Private constructor: prevent instances beyond my singleton.
+  MOZ_CONSTEXPR nsSMILFloatType() {}
 };
 
 #endif // NS_SMILFLOATTYPE_H_

--- a/content/smil/nsSMILNullType.h
+++ b/content/smil/nsSMILNullType.h
@@ -37,15 +37,13 @@ protected:
                                    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 & destructor: prevent instances beyond my singleton,
-  // and prevent others from deleting my singleton.
-  nsSMILNullType()  {}
-  ~nsSMILNullType() {}
+  // Private constructor: prevent instances beyond my singleton.
+  MOZ_CONSTEXPR nsSMILNullType() {}
 };
 
 #endif // NS_SMILNULLTYPE_H_

--- a/content/svg/content/src/SVGIntegerPairSMILType.h
+++ b/content/svg/content/src/SVGIntegerPairSMILType.h
@@ -38,17 +38,15 @@ protected:
                                    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 & destructor: prevent instances beyond my singleton,
-  // and prevent others from deleting my singleton.
-  SVGIntegerPairSMILType()  {}
-  ~SVGIntegerPairSMILType() {}
+  // Private constructor: prevent instances beyond my singleton.
+  MOZ_CONSTEXPR SVGIntegerPairSMILType() {}
 };
 
 } // namespace mozilla
 
 #endif // MOZILLA_SVGINTEGERPAIRSMILTYPE_H_

--- a/content/svg/content/src/SVGLengthListSMILType.h
+++ b/content/svg/content/src/SVGLengthListSMILType.h
@@ -86,17 +86,15 @@ protected:
                                    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 & destructor: prevent instances beyond my singleton,
-  // and prevent others from deleting my singleton.
-  SVGLengthListSMILType() {}
-  ~SVGLengthListSMILType() {}
+  // Private constructor: prevent instances beyond my singleton.
+  MOZ_CONSTEXPR SVGLengthListSMILType() {}
 };
 
 } // namespace mozilla
 
 #endif // MOZILLA_SVGLENGTHLISTSMILTYPE_H_

--- a/content/svg/content/src/SVGMotionSMILType.h
+++ b/content/svg/content/src/SVGMotionSMILType.h
@@ -66,17 +66,15 @@ public:
   // Used to generate a nsSMILValue for the point at the given distance along
   // the given path.
   static nsSMILValue ConstructSMILValue(gfxFlattenedPath* aPath,
                                         float aDist,
                                         RotateType aRotateType,
                                         float aRotateAngle);
 
 private:
-  // Private constructor & destructor: prevent instances beyond my singleton,
-  // and prevent others from deleting my singleton.
-  SVGMotionSMILType()  {}
-  ~SVGMotionSMILType() {}
+  // Private constructor: prevent instances beyond my singleton.
+  MOZ_CONSTEXPR SVGMotionSMILType() {}
 };
 
 } // namespace mozilla
 
 #endif // MOZILLA_SVGMOTIONSMILTYPE_H_

--- a/content/svg/content/src/SVGNumberListSMILType.h
+++ b/content/svg/content/src/SVGNumberListSMILType.h
@@ -40,17 +40,15 @@ protected:
                                    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 & destructor: prevent instances beyond my singleton,
-  // and prevent others from deleting my singleton.
-  SVGNumberListSMILType() {}
-  ~SVGNumberListSMILType() {}
+  // Private constructor: prevent instances beyond my singleton.
+  MOZ_CONSTEXPR SVGNumberListSMILType() {}
 };
 
 } // namespace mozilla
 
 #endif // MOZILLA_SVGNUMBERLISTSMILTYPE_H_

--- a/content/svg/content/src/SVGNumberPairSMILType.h
+++ b/content/svg/content/src/SVGNumberPairSMILType.h
@@ -33,17 +33,15 @@ protected:
                                    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 & destructor: prevent instances beyond my singleton,
-  // and prevent others from deleting my singleton.
-  SVGNumberPairSMILType()  {}
-  ~SVGNumberPairSMILType() {}
+  // Private constructor: prevent instances beyond my singleton.
+  MOZ_CONSTEXPR SVGNumberPairSMILType() {}
 };
 
 } // namespace mozilla
 
 #endif // MOZILLA_SVGNUMBERPAIRSMILTYPE_H_

--- a/content/svg/content/src/SVGOrientSMILType.h
+++ b/content/svg/content/src/SVGOrientSMILType.h
@@ -53,17 +53,15 @@ protected:
                                    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 & destructor: prevent instances beyond my singleton,
-  // and prevent others from deleting my singleton.
-  SVGOrientSMILType()  {}
-  ~SVGOrientSMILType() {}
+  // Private constructor: prevent instances beyond my singleton.
+  MOZ_CONSTEXPR SVGOrientSMILType() {}
 };
 
 } // namespace mozilla
 
 #endif // MOZILLA_SVGORIENTSMILTYPE_H_

--- a/content/svg/content/src/SVGPathSegListSMILType.h
+++ b/content/svg/content/src/SVGPathSegListSMILType.h
@@ -44,17 +44,15 @@ protected:
                                    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 & destructor: prevent instances beyond my singleton,
-  // and prevent others from deleting my singleton.
-  SVGPathSegListSMILType() {}
-  ~SVGPathSegListSMILType() {}
+  // Private constructor: prevent instances beyond my singleton.
+  MOZ_CONSTEXPR SVGPathSegListSMILType() {}
 };
 
 } // namespace mozilla
 
 #endif // MOZILLA_SVGPATHSEGLISTSMILTYPE_H_

--- a/content/svg/content/src/SVGPointListSMILType.h
+++ b/content/svg/content/src/SVGPointListSMILType.h
@@ -40,17 +40,15 @@ protected:
                                    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 & destructor: prevent instances beyond my singleton,
-  // and prevent others from deleting my singleton.
-  SVGPointListSMILType() {}
-  ~SVGPointListSMILType() {}
+  // Private constructor: prevent instances beyond my singleton.
+  MOZ_CONSTEXPR SVGPointListSMILType() {}
 };
 
 } // namespace mozilla
 
 #endif // MOZILLA_SVGPOINTLISTSMILTYPE_H_

--- a/content/svg/content/src/SVGTransformListSMILType.h
+++ b/content/svg/content/src/SVGTransformListSMILType.h
@@ -116,17 +116,15 @@ public:
                                   nsSMILValue& aValue);
   static bool AppendTransforms(const SVGTransformList& aList,
                                  nsSMILValue& aValue);
   static bool GetTransforms(const nsSMILValue& aValue,
                               FallibleTArray<nsSVGTransform>& aTransforms);
 
 
 private:
-  // Private constructor & destructor: prevent instances beyond my singleton,
-  // and prevent others from deleting my singleton.
-  SVGTransformListSMILType() {}
-  ~SVGTransformListSMILType() {}
+  // Private constructor: prevent instances beyond my singleton.
+  MOZ_CONSTEXPR SVGTransformListSMILType() {}
 };
 
 } // end namespace mozilla
 
 #endif // SVGLISTTRANSFORMSMILTYPE_H_

--- a/content/svg/content/src/SVGViewBoxSMILType.h
+++ b/content/svg/content/src/SVGViewBoxSMILType.h
@@ -33,17 +33,15 @@ protected:
                                    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 & destructor: prevent instances beyond my singleton,
-  // and prevent others from deleting my singleton.
-  SVGViewBoxSMILType()  {}
-  ~SVGViewBoxSMILType() {}
+  // Private constructor: prevent instances beyond my singleton.
+  MOZ_CONSTEXPR SVGViewBoxSMILType() {}
 };
 
 } // namespace mozilla
 
 #endif // MOZILLA_SVGVIEWBOXSMILTYPE_H_