Use just one marking deque.

src/heap/incremental-marking-inl.h

Index: src/heap/incremental-marking-inl.h
diff --git a/src/heap/incremental-marking-inl.h b/src/heap/incremental-marking-inl.h
index 5258c5c22ee5bfe19e5fa47eb65f9e20da241ed5..496e02d9550b16cc16c7110e99dd24d7253c89d3 100644
--- a/src/heap/incremental-marking-inl.h
+++ b/src/heap/incremental-marking-inl.h
@@ -103,13 +103,13 @@ void IncrementalMarking::BlackToGreyAndUnshift(HeapObject* obj,
     }
   }
 
-  marking_deque_.UnshiftGrey(obj);
+  heap_->mark_compact_collector()->marking_deque()->UnshiftGrey(obj);
 }
 
 
 void IncrementalMarking::WhiteToGreyAndPush(HeapObject* obj, MarkBit mark_bit) {
   Marking::WhiteToGrey(mark_bit);
-  marking_deque_.PushGrey(obj);
+  heap_->mark_compact_collector()->marking_deque()->PushGrey(obj);
 }
 }
 }  // namespace v8::internal