[Sync] Migrate bridge implementations to change list based MergeSyncData

components/sync/user_events/user_event_sync_bridge.cc

Index: components/sync/user_events/user_event_sync_bridge.cc
diff --git a/components/sync/user_events/user_event_sync_bridge.cc b/components/sync/user_events/user_event_sync_bridge.cc
index f601791b85c593b3c855c669e410b7b26746c723..ba5559e96bc43de8dcf6adf3ebf04af735b92e4c 100644
--- a/components/sync/user_events/user_event_sync_bridge.cc
+++ b/components/sync/user_events/user_event_sync_bridge.cc
@@ -76,7 +76,7 @@ UserEventSyncBridge::CreateMetadataChangeList() {
 
 base::Optional<ModelError> UserEventSyncBridge::MergeSyncData(
     std::unique_ptr<MetadataChangeList> metadata_change_list,
-    EntityDataMap entity_data_map) {
+    EntityChangeList entity_data) {
   NOTREACHED();
   return {};
 }