Revert of Force HostContentSettingsMap to be destroyed on its owning thread.

components/content_settings/core/browser/cookie_settings_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 "components/content_settings/core/browser/cookie_settings.h"
 
-#include "base/message_loop/message_loop.h"
 #include "components/content_settings/core/browser/host_content_settings_map.h"
 #include "components/content_settings/core/common/content_settings_pattern.h"
 #include "components/content_settings/core/common/pref_names.h"
 #include "components/sync_preferences/testing_pref_service_syncable.h"
 #include "extensions/features/features.h"
 #include "testing/gtest/include/gtest/gtest.h"
 #include "url/gurl.h"
 
 namespace content_settings {
 
@@ skipping 14 matching lines @@
     HostContentSettingsMap::RegisterProfilePrefs(prefs_.registry());
     settings_map_ = new HostContentSettingsMap(
         &prefs_, false /* incognito_profile */, false /* guest_profile */);
     cookie_settings_ =
         new CookieSettings(settings_map_.get(), &prefs_, "chrome-extension");
   }
 
   ~CookieSettingsTest() override { settings_map_->ShutdownOnUIThread(); }
 
  protected:
-  // There must be a valid ThreadTaskRunnerHandle in HostContentSettingsMap's
-  // scope.
-  base::MessageLoop message_loop_;
-
   sync_preferences::TestingPrefServiceSyncable prefs_;
   scoped_refptr<HostContentSettingsMap> settings_map_;
   scoped_refptr<CookieSettings> cookie_settings_;
   const GURL kBlockedSite;
   const GURL kAllowedSite;
   const GURL kFirstPartySite;
   const GURL kChromeURL;
   const GURL kExtensionURL;
   const GURL kHttpSite;
   const GURL kHttpsSite;
@@ skipping 179 matching lines @@
 
   // XHRs stemming from extensions are exempt from third-party cookie blocking
   // rules (as the first party is always the extension's security origin).
   EXPECT_TRUE(
       cookie_settings_->IsSettingCookieAllowed(kBlockedSite, kExtensionURL));
 }
 
 }  // namespace
 
 }  // namespace content_settings