[Sync] Refactor ModelSafeWorker::DoWorkAndWaitUntilDone() to avoid code duplication.

components/sync/engine/browser_thread_model_worker_unittest.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/browser_thread_model_worker.h"
 
 #include "base/bind.h"
 #include "base/callback.h"
 #include "base/location.h"
 #include "base/memory/weak_ptr.h"
@@ skipping 21 matching lines @@
   BrowserThreadModelWorker* worker() { return worker_.get(); }
   base::OneShotTimer* timer() { return &timer_; }
   base::WeakPtrFactory<SyncBrowserThreadModelWorkerTest>* factory() {
     return &weak_factory_;
   }
 
   // Schedule DoWork to be executed on the DB thread and have the test fail if
   // DoWork hasn't executed within action_timeout().
   void ScheduleWork() {
     // We wait until the callback is done. So it is safe to use unretained.
-    WorkCallback c = base::Bind(&SyncBrowserThreadModelWorkerTest::DoWork,
-                                base::Unretained(this));
     timer()->Start(FROM_HERE, TestTimeouts::action_timeout(), this,
                    &SyncBrowserThreadModelWorkerTest::Timeout);
-    worker()->DoWorkAndWaitUntilDone(c);
+    worker()->DoWorkAndWaitUntilDone(base::BindOnce(
+        &SyncBrowserThreadModelWorkerTest::DoWork, base::Unretained(this)));
   }
 
   // This is the work that will be scheduled to be done on the DB thread.
   SyncerError DoWork() {
     EXPECT_TRUE(db_thread_.task_runner()->BelongsToCurrentThread());
     main_message_loop_.task_runner()->PostTask(
         FROM_HERE, base::MessageLoop::QuitWhenIdleClosure());
     did_do_work_ = true;
     return SYNCER_OK;
   }
@@ skipping 31 matching lines @@
   base::ThreadTaskRunnerHandle::Get()->PostTask(
       FROM_HERE, base::Bind(&SyncBrowserThreadModelWorkerTest::ScheduleWork,
                             factory()->GetWeakPtr()));
   base::RunLoop().Run();
   EXPECT_TRUE(did_do_work());
 }
 
 }  // namespace
 
 }  // namespace syncer