Use ThreadChecker rather than DCHECK_CURRENTLY_ON.

chrome/browser/content_settings/host_content_settings_map.h

 // 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.
 
 // Maps hostnames to custom content settings.  Written on the UI thread and read
 // on any thread.  One instance per profile.
 
 #ifndef CHROME_BROWSER_CONTENT_SETTINGS_HOST_CONTENT_SETTINGS_MAP_H_
 #define CHROME_BROWSER_CONTENT_SETTINGS_HOST_CONTENT_SETTINGS_MAP_H_
 
 #include <map>
 #include <string>
 #include <vector>
 
 #include "base/basictypes.h"
 #include "base/memory/ref_counted.h"
 #include "base/observer_list.h"
 #include "base/prefs/pref_change_registrar.h"
 #include "base/threading/platform_thread.h"
+#include "base/threading/thread_checker.h"
 #include "base/tuple.h"
 #include "chrome/browser/content_settings/content_settings_override_provider.h"
 #include "components/content_settings/core/browser/content_settings_observer.h"
 #include "components/content_settings/core/common/content_settings.h"
 #include "components/content_settings/core/common/content_settings_pattern.h"
 #include "components/content_settings/core/common/content_settings_types.h"
 
 class ExtensionService;
 class GURL;
 class PrefService;
 
 namespace base {
 class Clock;
 class Value;
 }
 
 namespace content_settings {
 class OverrideProvider;
 class ObservableProvider;
 class ProviderInterface;
 class PrefProvider;
 }
 
 namespace user_prefs {
 class PrefRegistrySyncable;
 }
 
+// Note that HostContentSettingsMap assumes it's created on the UI thread.

[Bernhard Bauer, 2014/10/01 11:41:09]

Nit: Move this to the constructor, and change to match the style of the other
thread safety comments in here ("This should only be called on the UI thread").

[Jun Mukai, 2014/10/14 23:53:13]

Done.

 class HostContentSettingsMap
     : public content_settings::Observer,
       public base::RefCountedThreadSafe<HostContentSettingsMap> {
  public:
   enum ProviderType {
     // EXTENSION names is a layering violation when this class will move to
     // components.
     // TODO(mukai): find the solution.
     INTERNAL_EXTENSION_PROVIDER = 0,
     POLICY_PROVIDER,
@@ skipping 290 matching lines @@
   PrefService* prefs_;
 
   // Whether this settings map is for an OTR session.
   bool is_off_the_record_;
 
   // Content setting providers. This is only modified at construction
   // time and by RegisterExtensionService, both of which should happen
   // before any other uses of it.
   ProviderMap content_settings_providers_;
 
+  base::ThreadChecker thread_checker_;
+
   ObserverList<content_settings::Observer> observers_;
 
   DISALLOW_COPY_AND_ASSIGN(HostContentSettingsMap);
 };
 
 #endif  // CHROME_BROWSER_CONTENT_SETTINGS_HOST_CONTENT_SETTINGS_MAP_H_