Fixes bug in calculation of memory used by new space

runtime/vm/scavenger.cc

 // Copyright (c) 2011, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #include "vm/scavenger.h"
 
 #include "vm/dart.h"
 #include "vm/dart_api_state.h"
 #include "vm/isolate.h"
 #include "vm/lockers.h"
@@ skipping 930 matching lines @@
     }
   }
 
   Scavenge();
 
   // It is possible for objects to stay in the new space
   // if the VM cannot create more pages for these objects.
   ASSERT((UsedInWords() == 0) || failed_to_promote_);
 }
 
+int64_t Scavenger::UsedInWords() const {
+  uword saved_top = FlushTLS();
+  int64_t used_in_words = (top_ - FirstObjectStart()) >> kWordSizeLog2;
+  UnflushTLS(saved_top);
+  return used_in_words;
+}
+
 }  // namespace dart