Introduce an abstraction to write to a field.

src/objects.h

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 2592 matching lines @@
   // Transform slow named properties to fast variants.
   static void TransformToFastProperties(Handle<JSObject> object,
                                         int unused_property_fields);
 
   // Access fast-case object properties at index.
   static Handle<Object> FastPropertyAt(Handle<JSObject> object,
                                        Representation representation,
                                        int index);
   inline Object* RawFastPropertyAt(int index);
   inline void FastPropertyAtPut(int index, Object* value);
+  void WriteToField(int descriptor, Object* value);
 
   // Access to in object properties.
   inline int GetInObjectPropertyOffset(int index);
   inline Object* InObjectPropertyAt(int index);
   inline Object* InObjectPropertyAtPut(int index,
                                        Object* value,
                                        WriteBarrierMode mode
                                        = UPDATE_WRITE_BARRIER);
 
   // Set the object's prototype (only JSReceiver and null are allowed values).
@@ skipping 270 matching lines @@
 
   // Add a property to a fast-case object.
   static void AddFastProperty(Handle<JSObject> object,
                               Handle<Name> name,
                               Handle<Object> value,
                               PropertyAttributes attributes,
                               StoreFromKeyed store_mode,
                               ValueType value_type,
                               TransitionFlag flag);
 
+  static void MigrateToNewProperty(Handle<JSObject> object,
+                                   Handle<Map> transition,
+                                   Handle<Object> value);
+
   // Add a property to a slow-case object.
   static void AddSlowProperty(Handle<JSObject> object,
                               Handle<Name> name,
                               Handle<Object> value,
                               PropertyAttributes attributes);
 
   MUST_USE_RESULT static MaybeHandle<Object> DeleteProperty(
       Handle<JSObject> object,
       Handle<Name> name,
       DeleteMode mode);
@@ skipping 8129 matching lines @@
     } else {
       value &= ~(1 << bit_position);
     }
     return value;
   }
 };
 
 } }  // namespace v8::internal
 
 #endif  // V8_OBJECTS_H_