An object should only be promoted to the old generation if it survived a scavenge operation.

src/mark-compact.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_MARK_COMPACT_H_
 #define V8_MARK_COMPACT_H_
 
 #include "src/compiler-intrinsics.h"
 #include "src/spaces.h"
 
@@ skipping 852 matching lines @@
   //   After: Live objects are unmarked, non-live regions have been added to
   //          their space's free list. Active eden semispace is compacted by
   //          evacuation.
   //
 
   // If we are not compacting the heap, we simply sweep the spaces except
   // for the large object space, clearing mark bits and adding unmarked
   // regions to each space's free list.
   void SweepSpaces();
 
-  int DiscoverAndPromoteBlackObjectsOnPage(NewSpace* new_space,
+  int DiscoverAndEvacuateBlackObjectsOnPage(NewSpace* new_space,
                                            NewSpacePage* p);
 
   void EvacuateNewSpace();
 
   void EvacuateLiveObjectsFromPage(Page* p);
 
   void EvacuatePages();
 
   void EvacuateNewSpaceAndCandidates();
 
@@ skipping 92 matching lines @@
  private:
   MarkCompactCollector* collector_;
 };
 
 
 const char* AllocationSpaceName(AllocationSpace space);
 
 } }  // namespace v8::internal
 
 #endif  // V8_MARK_COMPACT_H_