[Sync] Move sync thread ownership to ProfileSyncService.

components/sync/driver/glue/sync_backend_registrar.cc

 // Copyright 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/driver/glue/sync_backend_registrar.h"
 
 #include <algorithm>
 #include <cstddef>
 #include <utility>
 
 #include "base/logging.h"
 #include "base/memory/ptr_util.h"
 #include "components/sync/driver/change_processor.h"
 #include "components/sync/driver/sync_client.h"
 #include "components/sync/syncable/user_share.h"
 
 namespace syncer {
 
 SyncBackendRegistrar::SyncBackendRegistrar(
     const std::string& name,
     SyncClient* sync_client,
-    std::unique_ptr<base::Thread> sync_thread,
     const scoped_refptr<base::SingleThreadTaskRunner>& ui_thread,
     const scoped_refptr<base::SingleThreadTaskRunner>& db_thread,
     const scoped_refptr<base::SingleThreadTaskRunner>& file_thread)
     : name_(name),
       sync_client_(sync_client),
       ui_thread_(ui_thread),
       db_thread_(db_thread),
       file_thread_(file_thread) {
   DCHECK(ui_thread_->BelongsToCurrentThread());
   DCHECK(sync_client_);
 
-  sync_thread_ = std::move(sync_thread);
-  if (!sync_thread_) {
-    sync_thread_ = base::MakeUnique<base::Thread>("Chrome_SyncThread");
-    base::Thread::Options options;
-    options.timer_slack = base::TIMER_SLACK_MAXIMUM;
-    CHECK(sync_thread_->StartWithOptions(options));
-  }
-
   MaybeAddWorker(GROUP_DB);
   MaybeAddWorker(GROUP_FILE);
   MaybeAddWorker(GROUP_UI);
   MaybeAddWorker(GROUP_PASSIVE);
   MaybeAddWorker(GROUP_HISTORY);
   MaybeAddWorker(GROUP_PASSWORD);
 
   // Must have at least one worker for SyncBackendRegistrar to be destroyed
   // correctly, as it is destroyed after the last worker dies.
   DCHECK_GT(workers_.size(), 0u);
@@ skipping 265 matching lines @@
 
 void SyncBackendRegistrar::MaybeAddWorker(ModelSafeGroup group) {
   const scoped_refptr<ModelSafeWorker> worker =
       sync_client_->CreateModelWorkerForGroup(group);
   if (worker) {
     DCHECK(workers_.find(group) == workers_.end());
     workers_[group] = worker;
   }
 }
 
-std::unique_ptr<base::Thread> SyncBackendRegistrar::ReleaseSyncThread() {
-  return std::move(sync_thread_);
-}
-
-base::Thread* SyncBackendRegistrar::sync_thread() {
-  return sync_thread_.get();
-}
-
 ModelSafeGroup SyncBackendRegistrar::GetInitialGroupForType(
     ModelType type) const {
   return non_blocking_types_.Has(type) ? GROUP_NON_BLOCKING : GROUP_PASSIVE;
 }
 
 }  // namespace syncer