Reland of [heap] Cleanup mark bit usage.

src/heap/spaces.cc

Index: src/heap/spaces.cc
diff --git a/src/heap/spaces.cc b/src/heap/spaces.cc
index 5a1ac65a2c7d4948ea426c7afd9afeafef603ac2..e94e87901f688d6056c2710131fcd59e09750581 100644
--- a/src/heap/spaces.cc
+++ b/src/heap/spaces.cc
@@ -3146,7 +3146,7 @@
   while (current != NULL) {
     HeapObject* object = current->GetObject();
     MarkBit mark_bit = Marking::MarkBitFrom(object);
-    DCHECK(Marking::IsBlackOrGrey(mark_bit));
+    DCHECK(Marking::IsBlack(mark_bit));
     Marking::BlackToWhite(mark_bit);
     Page::FromAddress(object->address())->ResetProgressBar();
     Page::FromAddress(object->address())->ResetLiveBytes();
@@ -3161,7 +3161,8 @@
   while (current != NULL) {
     HeapObject* object = current->GetObject();
     MarkBit mark_bit = Marking::MarkBitFrom(object);
-    if (Marking::IsBlackOrGrey(mark_bit)) {
+    DCHECK(!Marking::IsGrey(mark_bit));
+    if (Marking::IsBlack(mark_bit)) {
       previous = current;
       current = current->next_page();
     } else {