Integrate registry_hash_store_contents with the rest of tracked prefs.

components/user_prefs/tracked/registry_hash_store_contents_win.h

Index: components/user_prefs/tracked/registry_hash_store_contents_win.h
diff --git a/components/user_prefs/tracked/registry_hash_store_contents_win.h b/components/user_prefs/tracked/registry_hash_store_contents_win.h
index 580240f1b3b1085aefb4d3c248a76d9af4bc1d03..7d1db05fbedb1a3a261386582a43cabed64deaa4 100644
--- a/components/user_prefs/tracked/registry_hash_store_contents_win.h
+++ b/components/user_prefs/tracked/registry_hash_store_contents_win.h
@@ -18,6 +18,8 @@ class RegistryHashStoreContentsWin : public HashStoreContents {
                                         const base::string16& profile_name);
 
   // HashStoreContents overrides:
+  std::unique_ptr<HashStoreContents> MakeCopy() const override;
+  std::string GetUMASuffix() const override;
   void Reset() override;
   bool GetMac(const std::string& path, std::string* out_value) override;
   bool GetSplitMacs(const std::string& path,
@@ -36,6 +38,10 @@ class RegistryHashStoreContentsWin : public HashStoreContents {
   void SetSuperMac(const std::string& super_mac) override;
 
  private:
+  // Helper constructor for |MakeCopy|.
+  explicit RegistryHashStoreContentsWin(
+      const base::string16& preference_key_name);
+
   const base::string16 preference_key_name_;
 
   DISALLOW_COPY_AND_ASSIGN(RegistryHashStoreContentsWin);