[SyncFS] Construct and destruct sync_worker in worker_task_runner

chrome/browser/sync_file_system/drive_backend/drive_backend_sync_unittest.cc

 // Copyright 2014 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 <algorithm>
 #include <stack>
 
 #include "base/file_util.h"
 #include "base/message_loop/message_loop.h"
 #include "base/run_loop.h"
@@ skipping 64 matching lines @@
     fake_drive_service_helper_.reset(new FakeDriveServiceHelper(
         drive_service.get(), uploader.get(),
         kSyncRootFolderTitle));
 
     remote_sync_service_.reset(new SyncEngine(
         drive_service.PassAs<drive::DriveServiceInterface>(),
         uploader.Pass(),
         file_task_runner_.get(),
         NULL, NULL, NULL));
     remote_sync_service_->AddServiceObserver(this);
+
+    base::RunLoop run_loop;
     remote_sync_service_->Initialize(base_dir_.path(),
                                      base::MessageLoopProxy::current(),
+                                     run_loop.QuitClosure(),
                                      in_memory_env_.get());
+    run_loop.Run();
+
     remote_sync_service_->SetSyncEnabled(true);
-
     local_sync_service_->SetLocalChangeProcessor(remote_sync_service_.get());
     remote_sync_service_->SetRemoteChangeProcessor(local_sync_service_.get());
   }
 
   virtual void TearDown() OVERRIDE {
     typedef std::map<std::string, CannedSyncableFileSystem*>::iterator iterator;
     for (iterator itr = file_systems_.begin();
          itr != file_systems_.end(); ++itr) {
       itr->second->TearDown();
       delete itr->second;
@@ skipping 1475 matching lines @@
 
   EXPECT_EQ(1u, CountApp());
   EXPECT_EQ(1u, CountLocalFile(app_id));
 
   EXPECT_EQ(2u, CountMetadata());
   EXPECT_EQ(2u, CountTracker());
 }
 
 }  // namespace drive_backend
 }  // namespace sync_file_system