Mark the gonk SmsService class as final, no bug

dom/mobilemessage/src/gonk/SmsService.h

@@ -10,12 +10,13 @@
 #include "nsIRadioInterfaceLayer.h"
 #include "nsTArray.h"
 #include "nsString.h"
+#include "mozilla/Attributes.h"
 
 namespace mozilla {
 namespace dom {
 namespace mobilemessage {
 
-class SmsService : public nsISmsService
+class SmsService MOZ_FINAL : public nsISmsService
 {
 public:
   NS_DECL_ISUPPORTS