Integrate registry_hash_store_contents with the rest of tracked prefs.

components/user_prefs/tracked/hash_store_contents.h

Index: components/user_prefs/tracked/hash_store_contents.h
diff --git a/components/user_prefs/tracked/hash_store_contents.h b/components/user_prefs/tracked/hash_store_contents.h
index 91441c8fb91d5f904ece2420e6d8818e38fa9f17..7dc8680eef5e0a4e02f456257b6f734e2b7901c5 100644
--- a/components/user_prefs/tracked/hash_store_contents.h
+++ b/components/user_prefs/tracked/hash_store_contents.h
@@ -26,6 +26,15 @@ 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.