Use ThreadChecker rather than DCHECK_CURRENTLY_ON.

chrome/browser/content_settings/host_content_settings_map_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 "base/auto_reset.h"
 #include "base/command_line.h"
 #include "base/json/json_reader.h"
 #include "base/json/json_writer.h"
 #include "base/message_loop/message_loop.h"
 #include "base/prefs/pref_service.h"
 #include "base/prefs/scoped_user_pref_update.h"
 #include "chrome/browser/content_settings/content_settings_mock_observer.h"
 #include "chrome/browser/content_settings/cookie_settings.h"
 #include "chrome/browser/content_settings/host_content_settings_map.h"
 #include "chrome/browser/content_settings/mock_settings_observer.h"
-#include "chrome/common/chrome_switches.h"
 #include "chrome/common/pref_names.h"
 #include "chrome/common/url_constants.h"
 #include "chrome/test/base/testing_pref_service_syncable.h"
 #include "chrome/test/base/testing_profile.h"
 #include "components/content_settings/core/browser/content_settings_details.h"
 #include "content/public/test/test_browser_thread.h"
 #include "net/base/static_cookie_policy.h"
 #include "testing/gtest/include/gtest/gtest.h"
 #include "url/gurl.h"
 
@@ skipping 1049 matching lines @@
       CONTENT_SETTINGS_TYPE_IMAGES, true);
   EXPECT_EQ(CONTENT_SETTING_ALLOW,
             host_content_settings_map->GetContentSetting(
                 host, host, CONTENT_SETTINGS_TYPE_IMAGES, std::string()));
   host_content_settings_map->SetDefaultContentSetting(
       CONTENT_SETTINGS_TYPE_IMAGES, CONTENT_SETTING_BLOCK);
   EXPECT_EQ(CONTENT_SETTING_BLOCK,
             host_content_settings_map->GetContentSetting(
                 host, host, CONTENT_SETTINGS_TYPE_IMAGES, std::string()));
 }