Bug 1406440 - don't inline nsSMILNullType::Singleton(); r=dholbert

Defining Singleton() in the declaration of nsSMILNullType implicitly
sticks an "inline" on the function, which is not what we want: inlining
it spreads around a lot of static initialization code.  Providing an
out-of-line definition is much better in terms of code size.

dom/smil/nsSMILNullType.cpp

@@ -8,6 +8,13 @@
 #include "nsSMILValue.h"
 #include "nsDebug.h"
 
+/*static*/ nsSMILNullType*
+nsSMILNullType::Singleton()
+{
+  static nsSMILNullType sSingleton;
+  return &sSingleton;
+}
+
 nsresult
 nsSMILNullType::Assign(nsSMILValue& aDest, const nsSMILValue& aSrc) const
 {

dom/smil/nsSMILNullType.h

@@ -14,12 +14,7 @@ class nsSMILNullType : public nsISMILType
 {
 public:
   // Singleton for nsSMILValue objects to hold onto.
-  static nsSMILNullType*
-  Singleton()
-  {
-    static nsSMILNullType sSingleton;
-    return &sSingleton;
-  }
+  static nsSMILNullType* Singleton();
 
 protected:
   // nsISMILType Methods