Integrate registry_hash_store_contents with the rest of tracked prefs.

components/user_prefs/tracked/hash_store_contents.h

 // Copyright 2014 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 COMPONENTS_USER_PREFS_TRACKED_HASH_STORE_CONTENTS_H_
 #define COMPONENTS_USER_PREFS_TRACKED_HASH_STORE_CONTENTS_H_
 
 #include <map>
 #include <memory>
 #include <string>
 
 #include "base/strings/string_piece.h"
 
 namespace base {
 class DictionaryValue;
 class Value;
 }  // namespace base
 
 // Provides access to the contents of a preference hash store. The store
 // contains the following data:
 // Contents: a client-defined dictionary that should map preference names to
 // MACs.
 // Version: a client-defined version number for the format of Contents.
 // Super MAC: a MAC that authenticates the entirety of Contents.
 class HashStoreContents {
  public:
   virtual ~HashStoreContents() {}
 
+  // Returns true if this implementation of HashStoreContents can be copied via
+  // MakeCopy().
+  virtual bool IsCopyable() const = 0;
+
+  // Returns a copy of this HashStoreContents. Must only be called on
+  // lightweight implementations(which return true from IsCopyable()) and only

[gab, 2016/09/16 19:47:32]

Space between word and '('

[proberge, 2016/09/20 21:35:44]

Done.

+  // in scenarios where a copy cannot be avoided.
+  virtual std::unique_ptr<HashStoreContents> MakeCopy() const = 0;
+
   // Returns the suffix to be appended to UMA histograms for this store type.
   // The returned value must either be an empty string or one of the values in
   // histograms.xml's TrackedPreferencesExternalValidators.
   virtual base::StringPiece GetUMASuffix() const = 0;
 
   // Discards all data related to this hash store.
   virtual void Reset() = 0;
 
   // Outputs the MAC validating the preference at path. Returns true if a MAC
   // was successfully read and false otherwise.
@@ skipping 33 matching lines @@
   // Retrieves the super MAC value previously stored by SetSuperMac. May be
   // empty if no super MAC has been stored or if this store does not support
   // super MACs.
   virtual std::string GetSuperMac() const = 0;
 
   // Stores a super MAC value for this hash store.
   virtual void SetSuperMac(const std::string& super_mac) = 0;
 };
 
 #endif  // COMPONENTS_USER_PREFS_TRACKED_HASH_STORE_CONTENTS_H_