Switch BaseSessionService to use SequencedWorkerPool instead of FILE thread

chrome/browser/sessions/persistent_tab_restore_service_browsertest.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/sessions/persistent_tab_restore_service.h"
 
 #include "base/compiler_specific.h"
 #include "base/run_loop.h"
 #include "base/strings/stringprintf.h"
 #include "base/strings/utf_string_conversions.h"
+#include "base/threading/sequenced_worker_pool.h"
 #include "chrome/browser/chrome_notification_types.h"
 #include "chrome/browser/profiles/profile.h"
 #include "chrome/browser/sessions/session_service.h"
 #include "chrome/browser/sessions/session_service_factory.h"
 #include "chrome/browser/sessions/session_types.h"
 #include "chrome/browser/sessions/tab_restore_service_factory.h"
 #include "chrome/browser/sessions/tab_restore_service_observer.h"
 #include "chrome/browser/ui/browser_window.h"
 #include "chrome/common/url_constants.h"
 #include "chrome/test/base/chrome_render_view_host_test_harness.h"
@@ skipping 88 matching lines @@
     // Navigate back. We have to do this song and dance as NavigationController
     // isn't happy if you navigate immediately while going back.
     controller().GoToIndex(index);
     WebContentsTester::For(web_contents())->CommitPendingNavigation();
   }
 
   void RecreateService() {
     // Must set service to null first so that it is destroyed before the new
     // one is created.
     service_->Shutdown();
+    content::BrowserThread::GetBlockingPool()->FlushForTesting();
     service_.reset();
     service_.reset(new PersistentTabRestoreService(profile(), time_factory_));
     SynchronousLoadTabsFromLastSession();
   }
 
   // Adds a window with one tab and url to the profile's session service.
   // If |pinned| is true, the tab is marked as pinned in the session service.
   void AddWindowWithOneTabToSessionService(bool pinned) {
     SessionService* session_service =
         SessionServiceFactory::GetForProfile(profile());
@@ skipping 23 matching lines @@
 
     AddWindowWithOneTabToSessionService(pinned);
 
     // Set this, otherwise previous session won't be loaded.
     profile()->set_last_session_exited_cleanly(false);
   }
 
   void SynchronousLoadTabsFromLastSession() {
     // Ensures that the load is complete before continuing.
     service_->LoadTabsFromLastSession();
+    content::BrowserThread::GetBlockingPool()->FlushForTesting();
     base::RunLoop().RunUntilIdle();
+    content::BrowserThread::GetBlockingPool()->FlushForTesting();
   }
 
   GURL url1_;
   GURL url2_;
   GURL url3_;
   std::string user_agent_override_;
   scoped_ptr<PersistentTabRestoreService> service_;
   PersistentTabRestoreTimeFactory* time_factory_;
 };
 
@@ skipping 569 matching lines @@
 
   EXPECT_FALSE(service_->IsLoaded());
   TestTabRestoreServiceObserver observer;
   service_->AddObserver(&observer);
   EXPECT_EQ(max_entries, service_->entries().size());
   SynchronousLoadTabsFromLastSession();
   EXPECT_TRUE(observer.got_loaded());
   EXPECT_TRUE(service_->IsLoaded());
   service_->RemoveObserver(&observer);
 }