Factor out handling of mixed objects preprocessing after migration

src/heap/mark-compact.h

Index: src/heap/mark-compact.h
diff --git a/src/heap/mark-compact.h b/src/heap/mark-compact.h
index a5a5f02ee7cb4a0db6306b963d7fb36e46bd1896..097d4a1f2d62803191a2f11d870a6b345299e457 100644
--- a/src/heap/mark-compact.h
+++ b/src/heap/mark-compact.h
@@ -667,6 +667,10 @@ class MarkCompactCollector {
   void MigrateObject(HeapObject* dst, HeapObject* src, int size,
                      AllocationSpace to_old_space);
 
+  void MigrateObjectTagged(HeapObject* dst, HeapObject* src, int size);
+  void MigrateObjectMixed(HeapObject* dst, HeapObject* src, int size);
+  void MigrateObjectRaw(HeapObject* dst, HeapObject* src, int size);
+
   bool TryPromoteObject(HeapObject* object, int object_size);
 
   void InvalidateCode(Code* code);