Fix a race condition in ~RegistryHashStoreContentsWin

services/preferences/tracked/registry_hash_store_contents_win.h

Index: services/preferences/tracked/registry_hash_store_contents_win.h
diff --git a/services/preferences/tracked/registry_hash_store_contents_win.h b/services/preferences/tracked/registry_hash_store_contents_win.h
index 0b3b396205d60cda624442ace27e58a48357ce79..dd55669815790eabf4ab017c4e4b5f1280726c3d 100644
--- a/services/preferences/tracked/registry_hash_store_contents_win.h
+++ b/services/preferences/tracked/registry_hash_store_contents_win.h
@@ -8,18 +8,29 @@
 #include "base/macros.h"
 #include "base/strings/string16.h"
 #include "services/preferences/tracked/hash_store_contents.h"
+#include "services/preferences/tracked/temp_scoped_dir_cleaner.h"
+
+// Helper object to clear registry entries for scoped temporary pref stores.
+class TempScopedDirRegistryCleaner : public TempScopedDirCleaner {
+ public:
+  void SetRegistryPath(const base::string16& registry_path);
+
+ private:
+  friend class base::RefCountedThreadSafe<TempScopedDirRegistryCleaner>;
+  ~TempScopedDirRegistryCleaner() override;
+
+  base::string16 registry_path_;
+};
 
 // Implements HashStoreContents by storing MACs in the Windows registry.
 class RegistryHashStoreContentsWin : public HashStoreContents {
  public:
   // Constructs a RegistryHashStoreContents which acts on a registry entry
-  // defined by |registry_path| and |store_key|. If |store_key| begins with
-  // base::ScopedTempDir::GetTempDirPrefix(), this RegistryHashStoreContentsWin
-  // will self Reset() on destruction to avoid proliferating keys in tests that
-  // create a profile in a ScopedTempDir (https://crbug.com/721245).
-  explicit RegistryHashStoreContentsWin(const base::string16& registry_path,
-                                        const base::string16& store_key);
-
+  // defined by |registry_path| and |store_key|.
+  explicit RegistryHashStoreContentsWin(
+      const base::string16& registry_path,
+      const base::string16& store_key,
+      scoped_refptr<TempScopedDirCleaner> temp_dir_cleaner);
   ~RegistryHashStoreContentsWin() override;
 
   // HashStoreContents overrides:
@@ -49,7 +60,7 @@ class RegistryHashStoreContentsWin : public HashStoreContents {
       const RegistryHashStoreContentsWin& other);
 
   const base::string16 preference_key_name_;
-  const bool reset_on_delete_;
+  scoped_refptr<TempScopedDirCleaner> temp_dir_cleaner_;
 };
 
 #endif  // SERVICES_PREFERENCES_TRACKED_REGISTRY_HASH_STORE_CONTENTS_WIN_H_