Making MigrateToMap() a single bottleneck for all migrations except slow-to-fast case.

src/objects.h

 // Copyright 2012 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 "src/allocation.h"
 #include "src/assert-scope.h"
 #include "src/builtins.h"
@@ skipping 2614 matching lines @@
 
   static void MigrateToNewProperty(Handle<JSObject> object,
                                    Handle<Map> transition,
                                    Handle<Object> value);
 
  private:
   friend class DictionaryElementsAccessor;
   friend class JSReceiver;
   friend class Object;
 
+  static void MigrateFastToFast(Handle<JSObject> object, Handle<Map> new_map);
+  static void MigrateFastToSlow(Handle<JSObject> object,
+                                Handle<Map> new_map,
+                                int expected_additional_properties);
+
   static void UpdateAllocationSite(Handle<JSObject> object,
                                    ElementsKind to_kind);
 
   // Used from Object::GetProperty().
   MUST_USE_RESULT static MaybeHandle<Object> GetPropertyWithFailedAccessCheck(
       LookupIterator* it);
 
   MUST_USE_RESULT static MaybeHandle<Object> GetElementWithCallback(
       Handle<JSObject> object,
       Handle<Object> receiver,
@@ skipping 8502 matching lines @@
     } else {
       value &= ~(1 << bit_position);
     }
     return value;
   }
 };
 
 } }  // namespace v8::internal
 
 #endif  // V8_OBJECTS_H_