[Sync] Minor refactor around SyncCycle and ModelTypeSet usage.

components/sync/engine_impl/cycle/sync_cycle.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "components/sync/engine_impl/cycle/sync_cycle.h"
 
 #include <algorithm>
 #include <iterator>
 
 #include "base/logging.h"
 #include "base/memory/ptr_util.h"
 #include "components/sync/syncable/directory.h"
 
 namespace syncer {
 
-// static
-SyncCycle* SyncCycle::Build(SyncCycleContext* context, Delegate* delegate) {
-  return new SyncCycle(context, delegate);
-}
-
 SyncCycle::SyncCycle(SyncCycleContext* context, Delegate* delegate)
     : context_(context), delegate_(delegate) {
   status_controller_ = base::MakeUnique<StatusController>();
 }
 
 SyncCycle::~SyncCycle() {}
 
 SyncCycleSnapshot SyncCycle::TakeSnapshot() const {
   return TakeSnapshotWithSource(sync_pb::GetUpdatesCallerInfo::UNKNOWN);
 }
@@ skipping 47 matching lines @@
   for (auto& observer : *context_->listeners())
     observer.OnSyncCycleEvent(event);
 }
 
 void SyncCycle::SendProtocolEvent(const ProtocolEvent& event) {
   for (auto& observer : *context_->listeners())
     observer.OnProtocolEvent(event);
 }
 
 }  // namespace syncer