Lazily initialize MessageLoop for faster thread startup

chrome/browser/sync/glue/sync_backend_registrar_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 "chrome/browser/sync/glue/sync_backend_registrar.h"
 
 #include "base/run_loop.h"
 #include "chrome/browser/sync/glue/ui_model_worker.h"
 #include "chrome/test/base/testing_profile.h"
 #include "components/sync_driver/change_processor_mock.h"
@@ skipping 318 matching lines @@
   registrar->SetInitialTypes(ModelTypeSet());
 
   // Start the shutdown.
   registrar->RequestWorkerStopOnUIThread();
 
   sync_thread->message_loop()->PostTask(
       FROM_HERE,
       base::Bind(&SyncBackendRegistrar::Shutdown,
                  base::Unretained(registrar.release())));
 
+  // Make sure the thread starts running.
+  sync_thread->WaitUntilThreadStarted();
+
   // The test verifies that the sync thread doesn't block because
   // of the blocked DB thread and can finish the shutdown.
   sync_thread->message_loop()->RunUntilIdle();
 
   db_thread_lock_.Release();
 
   // Run the main thread loop until all workers have been removed and the
   // registrar destroyed.
   run_loop_.Run();
 }
 
 }  // namespace
 
 }  // namespace browser_sync