Integrate registry_hash_store_contents with the rest of tracked prefs.

components/user_prefs/tracked/dictionary_hash_store_contents.cc

Index: components/user_prefs/tracked/dictionary_hash_store_contents.cc
diff --git a/components/user_prefs/tracked/dictionary_hash_store_contents.cc b/components/user_prefs/tracked/dictionary_hash_store_contents.cc
index 1ee5770bc050b6d13e3c5a89d098af1b3e735a1f..49d24a7f7b93375f1993fbe1cceb45ea25e693fb 100644
--- a/components/user_prefs/tracked/dictionary_hash_store_contents.cc
+++ b/components/user_prefs/tracked/dictionary_hash_store_contents.cc
@@ -28,6 +28,18 @@ void DictionaryHashStoreContents::RegisterProfilePrefs(
   registry->RegisterStringPref(kSuperMACPref, std::string());
 }
 
+std::unique_ptr<HashStoreContents> DictionaryHashStoreContents::MakeCopy()
+    const {
+  NOTREACHED() << "DictionaryHashStoreContents does not support MakeCopy";
+  return nullptr;
+}
+
+std::string DictionaryHashStoreContents::GetUMASuffix() const {
+  // To stay consistent with existing reported data, do not append a suffix
+  // when reporting UMA stats for this content.
+  return "";
+}
+
 void DictionaryHashStoreContents::Reset() {
   storage_->Remove(kPreferenceMACs, NULL);
 }
@@ -115,4 +127,4 @@ base::DictionaryValue* DictionaryHashStoreContents::GetMutableContents(
     storage_->Set(kPreferenceMACs, macs_dict);
   }
   return macs_dict;
-}
+}