Use ThreadChecker rather than DCHECK_CURRENTLY_ON.

chrome/browser/content_settings/host_content_settings_map.h

Index: chrome/browser/content_settings/host_content_settings_map.h
diff --git a/chrome/browser/content_settings/host_content_settings_map.h b/chrome/browser/content_settings/host_content_settings_map.h
index dbe70c0d1338efa0a2685c37a16b9648c85e6696..fb119c27f5544b3443ee644fa6f372484d05a737 100644
--- a/chrome/browser/content_settings/host_content_settings_map.h
+++ b/chrome/browser/content_settings/host_content_settings_map.h
@@ -17,6 +17,7 @@
 #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"
@@ -44,6 +45,7 @@ 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> {
@@ -354,6 +356,8 @@ class HostContentSettingsMap
   // before any other uses of it.
   ProviderMap content_settings_providers_;
 
+  base::ThreadChecker thread_checker_;
+
   ObserverList<content_settings::Observer> observers_;
 
   DISALLOW_COPY_AND_ASSIGN(HostContentSettingsMap);