[heap] Fix live object iterator to skip grey filler objects.

src/heap/mark-compact.cc

Index: src/heap/mark-compact.cc
diff --git a/src/heap/mark-compact.cc b/src/heap/mark-compact.cc
index 427185a5c85fcae2a65df85b3b3db654150cb6de..c931f520b7aea13f03a45941eca58e76d05b65cb 100644
--- a/src/heap/mark-compact.cc
+++ b/src/heap/mark-compact.cc
@@ -104,7 +104,9 @@ static void VerifyMarking(Heap* heap, Address bottom, Address top) {
   Address next_object_must_be_here_or_later = bottom;
   for (Address current = bottom; current < top;) {
     object = HeapObject::FromAddress(current);
-    if (MarkCompactCollector::IsMarked(object)) {
+    // One word fillers at the end of a black area can be grey.
+    if (MarkCompactCollector::IsMarked(object) &&
+        object->map() != heap->one_pointer_filler_map()) {
       CHECK(Marking::IsBlack(ObjectMarking::MarkBitFrom(object)));
       CHECK(current >= next_object_must_be_here_or_later);
       object->Iterate(&visitor);