Fix a race condition in ~RegistryHashStoreContentsWin

services/preferences/tracked/temp_scoped_dir_cleaner.h

Index: services/preferences/tracked/temp_scoped_dir_cleaner.h
diff --git a/services/preferences/tracked/temp_scoped_dir_cleaner.h b/services/preferences/tracked/temp_scoped_dir_cleaner.h
new file mode 100644
index 0000000000000000000000000000000000000000..4359b760bd17be95cc14e1f83ad73294f2de2072
--- /dev/null
+++ b/services/preferences/tracked/temp_scoped_dir_cleaner.h
@@ -0,0 +1,18 @@
+// Copyright 2017 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef SERVICES_PREFERENCES_TRACKED_TEMP_SCOPED_DIR_CLEANER_H_
+#define SERVICES_PREFERENCES_TRACKED_TEMP_SCOPED_DIR_CLEANER_H_
+
+#include "base/memory/ref_counted.h"
+
+// Helper object to clear additional data for scoped temporary pref stores.
+class TempScopedDirCleaner
+    : public base::RefCountedThreadSafe<TempScopedDirCleaner> {
+ protected:
+  friend class base::RefCountedThreadSafe<TempScopedDirCleaner>;
+  virtual ~TempScopedDirCleaner(){};
+};
+
+#endif  // SERVICES_PREFERENCES_TRACKED_TEMP_SCOPED_DIR_CLEANER_H_