Add a premonomorphic state to the call target cache.

src/objects.h

Index: src/objects.h
diff --git a/src/objects.h b/src/objects.h
index bb98576eaff4464640b90cd20eeb28ee1d2309d9..9b292318f8b2fb40b750e7b75978d1a629c0da5c 100644
--- a/src/objects.h
+++ b/src/objects.h
@@ -8180,6 +8180,9 @@ class TypeFeedbackInfo: public Struct {
   // The object that indicates an uninitialized cache.
   static inline Handle<Object> UninitializedSentinel(Isolate* isolate);
 
+  // The object that indicates a cache in pre-monomorphic state.
+  static inline Handle<Object> PremonomorphicSentinel(Isolate* isolate);
+
   // The object that indicates a megamorphic state.
   static inline Handle<Object> MegamorphicSentinel(Isolate* isolate);