Integrate registry_hash_store_contents with the rest of tracked prefs.

components/user_prefs/tracked/pref_hash_store_impl.h

Index: components/user_prefs/tracked/pref_hash_store_impl.h
diff --git a/components/user_prefs/tracked/pref_hash_store_impl.h b/components/user_prefs/tracked/pref_hash_store_impl.h
index 4a2520f0d891f71f63a029a372706205f1bc5ab1..d5a217f321ce1ceca01c47b80029569cd0cc3d2b 100644
--- a/components/user_prefs/tracked/pref_hash_store_impl.h
+++ b/components/user_prefs/tracked/pref_hash_store_impl.h
@@ -16,6 +16,11 @@
 class HashStoreContents;
 class PrefHashStoreTransaction;
 
+namespace base {
+class DictionaryValue;
+class Value;
+}  // namespace base
+
 // Implements PrefHashStoreImpl by storing preference hashes in a
 // HashStoreContents.
 class PrefHashStoreImpl : public PrefHashStore {
@@ -49,6 +54,13 @@ class PrefHashStoreImpl : public PrefHashStore {
   std::unique_ptr<PrefHashStoreTransaction> BeginTransaction(
       std::unique_ptr<HashStoreContents> storage) override;
 
+  std::string ComputeMac(const std::string& path,
+                         const base::Value* new_value) override;
+
+  std::unique_ptr<base::DictionaryValue> ComputeSplitMacs(
+      const std::string& path,
+      const base::DictionaryValue* split_values) override;
+
  private:
   class PrefHashStoreTransactionImpl;