Ensure black and gray objects are kept around by scavenger

src/heap/incremental-marking.cc

Index: src/heap/incremental-marking.cc
diff --git a/src/heap/incremental-marking.cc b/src/heap/incremental-marking.cc
index c250b90b1c99d260be6ae137d212ca02bc97db35..83750346983884afd1b5c1833af55cf054d70807 100644
--- a/src/heap/incremental-marking.cc
+++ b/src/heap/incremental-marking.cc
@@ -806,9 +806,9 @@ void IncrementalMarking::UpdateMarkingDequeAfterScavenge() {
         new_top = ((new_top + 1) & mask);
         DCHECK(new_top != marking_deque->bottom());
 #ifdef DEBUG
+        // Mark bit of the source object should be cleared
         MarkBit mark_bit = Marking::MarkBitFrom(obj);
-        DCHECK(Marking::IsGrey(mark_bit) ||
-               (obj->IsFiller() && Marking::IsWhite(mark_bit)));
+        DCHECK(Marking::IsWhite(mark_bit));
 #endif
       }
     } else if (obj->map() != filler_map) {