Reland of [heap] Unify evacuating an object for new and old generation.

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 cf3b3a68c03f730a1b0773ba6a50011f55aa33cf..3386b83272bfdb8572d86568fac4e3e2b3258e3a 100644
--- a/src/heap/mark-compact.h
+++ b/src/heap/mark-compact.h
@@ -326,10 +326,6 @@
     kClearMarkbits,
   };
 
-  class EvacuateNewSpaceVisitor;
-  class EvacuateOldSpaceVisitor;
-  class HeapObjectVisitor;
-
   static void Initialize();
 
   void SetUp();
@@ -417,8 +413,6 @@
                      AllocationSpace to_old_space,
                      SlotsBuffer** evacuation_slots_buffer);
 
-  bool TryPromoteObject(HeapObject* object, int object_size);
-
   void InvalidateCode(Code* code);
 
   void ClearMarkbits();
@@ -516,6 +510,10 @@
 
  private:
   class CompactionTask;
+  class EvacuateNewSpaceVisitor;
+  class EvacuateOldSpaceVisitor;
+  class EvacuateVisitorBase;
+  class HeapObjectVisitor;
   class SweeperTask;
 
   explicit MarkCompactCollector(Heap* heap);