[SyncFS] Construct and destruct sync_worker in worker_task_runner

chrome/browser/sync_file_system/drive_backend/sync_engine_unittest.cc

 // Copyright 2013 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 "chrome/browser/sync_file_system/drive_backend/sync_engine.h"
 
 #include "base/files/scoped_temp_dir.h"
 #include "base/run_loop.h"
 #include "base/strings/stringprintf.h"
 #include "chrome/browser/drive/drive_uploader.h"
@@ skipping 100 matching lines @@
     scoped_ptr<drive::DriveServiceInterface>
         fake_drive_service(new drive::FakeDriveService);
 
     sync_engine_.reset(new drive_backend::SyncEngine(
         fake_drive_service.Pass(),
         scoped_ptr<drive::DriveUploaderInterface>(),
         base::MessageLoopProxy::current(),
         NULL /* notification_manager */,
         extension_service_.get(),
         NULL /* signin_manager */));
+
+    base::RunLoop run_loop;
     sync_engine_->Initialize(profile_dir_.path(),
                              base::MessageLoopProxy::current(),
+                             run_loop.QuitClosure(),
                              in_memory_env_.get());
+    run_loop.Run();
     sync_engine_->SetSyncEnabled(true);
     base::RunLoop().RunUntilIdle();
   }
 
   virtual void TearDown() OVERRIDE {
     sync_engine_.reset();
     extension_service_.reset();
     base::RunLoop().RunUntilIdle();
   }
 
@@ skipping 240 matching lines @@
       base::Bind(&SyncEngineTest::CheckServiceState,
                  AsWeakPtr(),
                  SYNC_STATUS_OK,
                  REMOTE_SERVICE_OK));
 
   base::RunLoop().RunUntilIdle();
 }
 
 }  // namespace drive_backend
 }  // namespace sync_file_system