[Sync] Minor refactor around SyncCycle and ModelTypeSet usage.

components/sync/engine_impl/syncer_unittest.cc

Index: components/sync/engine_impl/syncer_unittest.cc
diff --git a/components/sync/engine_impl/syncer_unittest.cc b/components/sync/engine_impl/syncer_unittest.cc
index 01713f58f9da64fa5481c049a8930010c29a5fca..27702c29de4ab51caca020276fe03773944ff40a 100644
--- a/components/sync/engine_impl/syncer_unittest.cc
+++ b/components/sync/engine_impl/syncer_unittest.cc
@@ -238,7 +238,9 @@ class SyncerTest : public testing::Test,
   void OnBackedOffTypesChanged(ModelTypeSet backed_off_types) override {}
   void OnMigrationRequested(ModelTypeSet types) override {}
 
-  void ResetCycle() { cycle_.reset(SyncCycle::Build(context_.get(), this)); }
+  void ResetCycle() {
+    cycle_ = base::MakeUnique<SyncCycle>(context_.get(), this);
+  }
 
   bool SyncShareNudge() {
     ResetCycle();