Bug 774037 - Fix -Wdelete-non-virtual-dtor warning. r=dolske.

toolkit/identity/IdentityCryptoService.cpp

@@ -208,7 +208,7 @@ private:
   void operator=(const SignRunnable &) MOZ_DELETE;
 };
 
-class IdentityCryptoService : public nsIIdentityCryptoService
+class IdentityCryptoService MOZ_FINAL : public nsIIdentityCryptoService
 {
 public:
   NS_DECL_ISUPPORTS