--- old/src/share/vm/utilities/bitMap.hpp	2019-01-28 17:44:59.000000000 +0800
+++ new/src/share/vm/utilities/bitMap.hpp	2019-01-28 17:44:59.000000000 +0800
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 1997, 2013, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 1997, 2019, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -272,6 +272,15 @@
 #endif
 };
 
+// A concrete implementation of the the "abstract" BitMap class.
+//
+// The BitMapView is used when the backing storage is managed externally.
+class BitMapView : public BitMap {
+ public:
+  BitMapView() : BitMap((bm_word_t*)NULL, (idx_t)0) {}
+  BitMapView(bm_word_t* map, idx_t size_in_bits) : BitMap(map, size_in_bits) {}
+};
+
 // Convenience class wrapping BitMap which provides multiple bits per slot.
 class BitMap2D VALUE_OBJ_CLASS_SPEC {
  public: