Make sure we don't accidentially serialize type feedback

src/type-feedback-vector.h

Index: src/type-feedback-vector.h
diff --git a/src/type-feedback-vector.h b/src/type-feedback-vector.h
index 864f336f90cb733f3e2ce28d875383bc25782231..d1d48db0535d893d1a43151acbd18d69ab834807 100644
--- a/src/type-feedback-vector.h
+++ b/src/type-feedback-vector.h
@@ -166,6 +166,9 @@ class TypeFeedbackVector : public FixedArray {
   // Clears the vector slots and the vector ic slots.
   void ClearSlots(SharedFunctionInfo* shared);
 
+  // Returns true if all slots are clear.
+  bool IsCleared();
+
   // The object that indicates an uninitialized cache.
   static inline Handle<Object> UninitializedSentinel(Isolate* isolate);