Bug 1273669. Make JS::CustomAutoRooter::Inner final. r=billm

Fixes clang virtual destructor warnings.

js/src/vm/Shape.h

@@ -1010,7 +1010,7 @@ StackBaseShape::StackBaseShape(Shape* shape)
 
 class MOZ_RAII AutoRooterGetterSetter
 {
-    class Inner : private JS::CustomAutoRooter
+    class Inner final : private JS::CustomAutoRooter
     {
       public:
         inline Inner(ExclusiveContext* cx, uint8_t attrs, GetterOp* pgetter_, SetterOp* psetter_);