Remove PROHIBITS_OVERWRITING as it is subsumed by non-configurable properties.

src/objects.h

Index: src/objects.h
diff --git a/src/objects.h b/src/objects.h
index 401ce404ac31d06e275a0fa7eaa5e57b883ff5b7..1082b71bdfa5efa1617b400a8c7d25941c5fa979 100644
--- a/src/objects.h
+++ b/src/objects.h
@@ -2441,7 +2441,6 @@ class JSObject: public JSReceiver {
   void LookupRealNamedProperty(Handle<Name> name, LookupResult* result);
   void LookupRealNamedPropertyInPrototypes(Handle<Name> name,
                                            LookupResult* result);
-  void LookupCallbackProperty(Handle<Name> name, LookupResult* result);
 
   // Returns the number of properties on this object filtering out properties
   // with the specified attributes (ignoring interceptors).
@@ -10373,9 +10372,6 @@ class AccessorInfo: public Struct {
   inline bool all_can_write();
   inline void set_all_can_write(bool value);
 
-  inline bool prohibits_overwriting();
-  inline void set_prohibits_overwriting(bool value);
-
   inline PropertyAttributes property_attributes();
   inline void set_property_attributes(PropertyAttributes attributes);
 
@@ -10402,8 +10398,7 @@ class AccessorInfo: public Struct {
   // Bit positions in flag.
   static const int kAllCanReadBit = 0;
   static const int kAllCanWriteBit = 1;
-  static const int kProhibitsOverwritingBit = 2;
-  class AttributesField: public BitField<PropertyAttributes, 3, 3> {};
+  class AttributesField: public BitField<PropertyAttributes, 2, 3> {};
 
   DISALLOW_IMPLICIT_CONSTRUCTORS(AccessorInfo);
 };
@@ -10568,7 +10563,6 @@ class AccessorPair: public Struct {
   inline void set_access_flags(v8::AccessControl access_control);
   inline bool all_can_read();
   inline bool all_can_write();
-  inline bool prohibits_overwriting();
 
   static inline AccessorPair* cast(Object* obj);
 
@@ -10611,7 +10605,6 @@ class AccessorPair: public Struct {
  private:
   static const int kAllCanReadBit = 0;
   static const int kAllCanWriteBit = 1;
-  static const int kProhibitsOverwritingBit = 2;
 
   // Strangely enough, in addition to functions and harmony proxies, the spec
   // requires us to consider undefined as a kind of accessor, too: