Revert of [heap] Make non-atomic markbit operations consistent with atomic ones.

src/heap/incremental-marking.h

Index: src/heap/incremental-marking.h
diff --git a/src/heap/incremental-marking.h b/src/heap/incremental-marking.h
index 14dce2c867e14fb14ebeaf503445e8f2923cce3f..c777693d6341942fb4bcfbdc80c2b2e3c1264266 100644
--- a/src/heap/incremental-marking.h
+++ b/src/heap/incremental-marking.h
@@ -65,6 +65,9 @@
     return MarkingState::Internal(chunk);
   }
 
+  void MarkBlack(HeapObject* object, int size);
+  void MarkGrey(HeapObject* object);
+
   // Transfers mark bits without requiring proper object headers.
   void TransferMark(Heap* heap, HeapObject* from, HeapObject* to);
 
@@ -79,15 +82,9 @@
 
     DCHECK(ObjectMarking::IsWhite<access_mode>(to, marking_state(to)));
     if (ObjectMarking::IsGrey<access_mode>(from, marking_state(from))) {
-      bool success =
-          ObjectMarking::WhiteToGrey<access_mode>(to, marking_state(to));
-      DCHECK(success);
-      USE(success);
+      ObjectMarking::WhiteToGrey<access_mode>(to, marking_state(to));
     } else if (ObjectMarking::IsBlack<access_mode>(from, marking_state(from))) {
-      bool success =
-          ObjectMarking::WhiteToBlack<access_mode>(to, marking_state(to));
-      DCHECK(success);
-      USE(success);
+      ObjectMarking::WhiteToBlack<access_mode>(to, marking_state(to));
     }
   }
 
@@ -213,9 +210,7 @@
   void RecordCodeTargetPatch(Code* host, Address pc, HeapObject* value);
   void RecordCodeTargetPatch(Address pc, HeapObject* value);
 
-  // Returns true if the function succeeds in transitioning the object
-  // from white to grey.
-  bool WhiteToGreyAndPush(HeapObject* obj);
+  void WhiteToGreyAndPush(HeapObject* obj);
 
   inline void SetOldSpacePageFlags(MemoryChunk* chunk) {
     SetOldSpacePageFlags(chunk, IsMarking(), IsCompacting());