Ensure tests have an active task runner

chrome/browser/sync/profile_sync_service_factory_unittest.cc

 // Copyright (c) 2015 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 "base/command_line.h"
 #include "base/memory/scoped_ptr.h"
 #include "chrome/browser/sync/profile_sync_service_factory.h"
 #include "chrome/common/chrome_switches.h"
 #include "chrome/test/base/testing_profile.h"
+#include "content/public/test/test_browser_thread_bundle.h"
 #include "testing/gtest/include/gtest/gtest.h"
 
 class ProfileSyncServiceFactoryTest : public testing::Test {
  protected:
   ProfileSyncServiceFactoryTest() {}
 
   void SetUp() override {
     profile_.reset(new TestingProfile());
   }
 
+  content::TestBrowserThreadBundle thread_bundle_;
   scoped_ptr<Profile> profile_;
 };
 
 // Verify that the disable sync flag disables creation of the sync service.
 TEST_F(ProfileSyncServiceFactoryTest, DisableSyncFlag) {
   base::CommandLine::ForCurrentProcess()->AppendSwitch(switches::kDisableSync);
   EXPECT_EQ(nullptr, ProfileSyncServiceFactory::GetForProfile(profile_.get()));
 }