Switch BaseSessionService to use SequencedWorkerPool instead of FILE thread

chrome/browser/sessions/session_service_test_helper.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/session_service_test_helper.h"
 
 #include "base/memory/scoped_vector.h"
 #include "chrome/browser/sessions/session_backend.h"
 #include "chrome/browser/sessions/session_id.h"
 #include "chrome/browser/sessions/session_service.h"
 #include "chrome/browser/sessions/session_types.h"
 #include "components/sessions/serialized_navigation_entry_test_helper.h"
+#include "content/public/browser/browser_thread.h"
 #include "testing/gtest/include/gtest/gtest.h"
 
 using base::Time;
 
 SessionServiceTestHelper::SessionServiceTestHelper() {}
 
 SessionServiceTestHelper::SessionServiceTestHelper(SessionService* service)
     : service_(service) {}
 
 SessionServiceTestHelper::~SessionServiceTestHelper() {}
@@ skipping 73 matching lines @@
     const std::vector<SessionWindow*>& windows,
     size_t nav_count) {
   ASSERT_EQ(1U, windows.size());
   EXPECT_EQ(1U, windows[0]->tabs.size());
   EXPECT_EQ(nav_count, windows[0]->tabs[0]->navigations.size());
 }
 
 SessionBackend* SessionServiceTestHelper::backend() {
   return service_->backend();
 }
+
+void SessionServiceTestHelper::SetService(SessionService* service) {
+  service_.reset(service);
+  // Execute IO tasks posted by the SessionService.
+  content::BrowserThread::GetBlockingPool()->FlushForTesting();
+}
+