Use ThreadChecker rather than DCHECK_CURRENTLY_ON.

chrome/browser/content_settings/content_settings_override_provider.h

 // Copyright 2014 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.
 
 #ifndef CHROME_BROWSER_CONTENT_SETTINGS_CONTENT_SETTINGS_OVERRIDE_PROVIDER_H_
 #define CHROME_BROWSER_CONTENT_SETTINGS_CONTENT_SETTINGS_OVERRIDE_PROVIDER_H_
 
 #include "base/macros.h"
 #include "base/synchronization/lock.h"
+#include "base/threading/thread_checker.h"
 #include "components/content_settings/core/browser/content_settings_provider.h"
 #include "components/content_settings/core/common/content_settings_types.h"
 
 class ContentSettingsPattern;
 class PrefService;
 
 namespace user_prefs {
 class PrefRegistrySyncable;
 }
 
@@ skipping 41 matching lines @@
   bool allowed_settings_[CONTENT_SETTINGS_NUM_TYPES];
 
   PrefService* prefs_;
 
   bool is_incognito_;
 
   // Used around accesses to the |override_content_settings_| object to
   // guarantee thread safety.
   mutable base::Lock lock_;
 
+  base::ThreadChecker thread_checker_;
+
   DISALLOW_COPY_AND_ASSIGN(OverrideProvider);
 };
 
 }  // namespace content_settings
 
 #endif  // CHROME_BROWSER_CONTENT_SETTINGS_CONTENT_SETTINGS_OVERRIDE_PROVIDER_H_