Bug 856344 - Fix getAllocKind() in TradeGuts (r=bhackett)

js/src/jsobj.cpp

@@ -1826,7 +1826,7 @@ JSObject::ReserveForTradeGuts(JSContext *cx, JSObject *aArg, JSObject *bArg,
             return false;
     } else {
         reserved.newbshape = EmptyShape::getInitialShape(cx, aClass, aProto, a->getParent(),
-                                                         b->numFixedSlots());
+                                                         b->tenuredGetAllocKind());
         if (!reserved.newbshape)
             return false;
     }
@@ -1835,7 +1835,7 @@ JSObject::ReserveForTradeGuts(JSContext *cx, JSObject *aArg, JSObject *bArg,
             return false;
     } else {
         reserved.newashape = EmptyShape::getInitialShape(cx, bClass, bProto, b->getParent(),
-                                                         a->numFixedSlots());
+                                                         a->tenuredGetAllocKind());
         if (!reserved.newashape)
             return false;
     }