MarkBit cleanup: They have to be accessed through Marking accessors.

src/heap/store-buffer.cc

Index: src/heap/store-buffer.cc
diff --git a/src/heap/store-buffer.cc b/src/heap/store-buffer.cc
index 6bf318871754d3d642bcd8dba58cbb7bc9bb0912..f7af1d0487b87e243ab257eebc2a0a9c16f556c3 100644
--- a/src/heap/store-buffer.cc
+++ b/src/heap/store-buffer.cc
@@ -380,7 +380,8 @@ void StoreBuffer::ClearInvalidStoreBufferEntries() {
   LargeObjectIterator it(heap_->lo_space());
   for (HeapObject* object = it.Next(); object != NULL; object = it.Next()) {
     MemoryChunk* chunk = MemoryChunk::FromAddress(object->address());
-    if (chunk->scan_on_scavenge() && !Marking::MarkBitFrom(object).Get()) {
+    if (chunk->scan_on_scavenge() &&
+        Marking::IsWhite(Marking::MarkBitFrom(object))) {
       chunk->set_scan_on_scavenge(false);
     }
   }