Remove usage of FOR_EACH_OBSERVER macro in components/sync

components/sync/driver/backend_migrator.cc

Index: components/sync/driver/backend_migrator.cc
diff --git a/components/sync/driver/backend_migrator.cc b/components/sync/driver/backend_migrator.cc
index 4a2d01942942986242bba056fb6ca84728482e4a..7edbbaf9bf03fbf22f33c8b250b71787ad049112 100644
--- a/components/sync/driver/backend_migrator.cc
+++ b/components/sync/driver/backend_migrator.cc
@@ -81,8 +81,8 @@ void BackendMigrator::RemoveMigrationObserver(MigrationObserver* observer) {
 
 void BackendMigrator::ChangeState(State new_state) {
   state_ = new_state;
-  FOR_EACH_OBSERVER(MigrationObserver, migration_observers_,
-                    OnMigrationStateChange());
+  for (auto& observer : migration_observers_)
+    observer.OnMigrationStateChange();
 }
 
 bool BackendMigrator::TryStart() {