Keep representations while overwriting transitions.

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 236 matching lines @@
 // Indicates whether a get method should implicitly create the object looked up.
 enum CreationFlag {
   ALLOW_CREATION,
   OMIT_CREATION
 };
 
 
 // Indicates whether transitions can be added to a source map or not.
 enum TransitionFlag {
   INSERT_TRANSITION,
+  OMIT_TRANSITION_KEEP_REPRESENTATIONS,
   OMIT_TRANSITION
 };
 
 
 enum DebugExtraICState {
   DEBUG_BREAK,
   DEBUG_PREPARE_STEP_IN
 };
 
 
@@ skipping 1926 matching lines @@
       int transition_index,
       Name* name,
       Object* new_value,
       PropertyAttributes attributes);
 
   // Converts a descriptor of any other type to a real field, backed by the
   // properties array.
   MUST_USE_RESULT MaybeObject* ConvertDescriptorToField(
       Name* name,
       Object* new_value,
-      PropertyAttributes attributes);
+      PropertyAttributes attributes,
+      TransitionFlag flag = OMIT_TRANSITION);
 
   MUST_USE_RESULT MaybeObject* MigrateToMap(Map* new_map);
   MUST_USE_RESULT MaybeObject* GeneralizeFieldRepresentation(
       int modify_index,
       Representation new_representation);
 
   // Add a property to a fast-case object.
   MUST_USE_RESULT MaybeObject* AddFastProperty(
       Name* name,
       Object* value,
@@ skipping 7393 matching lines @@
     } else {
       value &= ~(1 << bit_position);
     }
     return value;
   }
 };
 
 } }  // namespace v8::internal
 
 #endif  // V8_OBJECTS_H_