Revert part of 11727 as it sometimes tanked V8 benchmark (raytrace) performance

src/objects.h

Index: src/objects.h
===================================================================
--- src/objects.h	(revision 11828)
+++ src/objects.h	(working copy)
@@ -4749,14 +4749,6 @@
   inline void set_is_shared(bool value);
   inline bool is_shared();
 
-  // Tells whether the map is used for an object that is a prototype for another
-  // object or is the prototype on a function.  Such maps are made faster by
-  // tweaking the heuristics that distinguish between regular object-oriented
-  // objects and the objects that are being used as hash maps.  This flag is
-  // for optimization, not correctness.
-  inline void set_used_for_prototype(bool value);
-  inline bool used_for_prototype();
-
   // Tells whether the instance needs security checks when accessing its
   // properties.
   inline void set_is_access_check_needed(bool access_check_needed);
@@ -4944,9 +4936,7 @@
   // the original map.  That way we can transition to the same map if the same
   // prototype is set, rather than creating a new map every time.  The
   // transitions are in the form of a map where the keys are prototype objects
-  // and the values are the maps the are transitioned to.  The special key
-  // the_hole denotes the map we should transition to when the
-  // used_for_prototype flag is set.
+  // and the values are the maps the are transitioned to.
   static const int kMaxCachedPrototypeTransitions = 256;
 
   Map* GetPrototypeTransition(Object* prototype);
@@ -5042,7 +5032,6 @@
   // Bit positions for bit field 3
   static const int kIsShared = 0;
   static const int kFunctionWithPrototype = 1;
-  static const int kUsedForPrototype = 2;
 
   typedef FixedBodyDescriptor<kPointerFieldsBeginOffset,
                               kPointerFieldsEndOffset,