[FeedbackVector] Clarify the way the feedback vector is installed.

src/objects.h

 // Copyright 2015 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef V8_OBJECTS_H_
 #define V8_OBJECTS_H_
 
 #include <iosfwd>
 #include <memory>
 
@@ skipping 8049 matching lines @@
 
   // Tells whether or not the function is on the concurrent recompilation queue.
   inline bool IsInOptimizationQueue();
 
   // Completes inobject slack tracking on initial map if it is active.
   inline void CompleteInobjectSlackTrackingIfActive();
 
   // [feedback_vector_cell]: Fixed array holding the feedback vector.
   DECL_ACCESSORS(feedback_vector_cell, Cell)
 
+  enum FeedbackVectorState {
+    TOP_LEVEL_SCRIPT_NEEDS_VECTOR,
+    NEEDS_VECTOR,
+    HAS_VECTOR
+  };
+
+  inline FeedbackVectorState GetFeedbackVectorState(Isolate* isolate) const;
+
   // feedback_vector() can be used once the function is compiled.
   inline FeedbackVector* feedback_vector() const;
   inline bool has_feedback_vector() const;
   static void EnsureLiterals(Handle<JSFunction> function);
 
   // Unconditionally clear the type feedback vector (including vector ICs).
   void ClearTypeFeedbackInfo();
 
   // Clear the type feedback vector with a more subtle policy at GC time.
   void ClearTypeFeedbackInfoAtGCTime();
@@ skipping 3543 matching lines @@
   }
 };
 
 
 }  // NOLINT, false-positive due to second-order macros.
 }  // NOLINT, false-positive due to second-order macros.
 
 #include "src/objects/object-macros-undef.h"
 
 #endif  // V8_OBJECTS_H_