Make ExtensionContentSettingsStore refcounted.

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 a4ed56faf5eb6d8f988c7afafa3adeab37a3e625..816b746220a9589239cb3ae35d31a2020b4d90f0 100644
--- a/chrome/browser/content_settings/host_content_settings_map.h
+++ b/chrome/browser/content_settings/host_content_settings_map.h
@@ -187,6 +187,12 @@ class HostContentSettingsMap
   // Returns true if the default setting for the |content_type| is managed.
   bool IsDefaultContentSettingManaged(ContentSettingsType content_type) const;
 
+  // Detaches the HostContentSettingsMap from all Profile-related objects like
+  // PrefService. This methods needs to be called before destroying the Profile.
+  // Afterwards, none of the methods above that should only be called on the UI
+  // thread should be called anymore.
+  void ShutdownOnUIThread();
+
   // NotificationObserver implementation.
   virtual void Observe(NotificationType type,
                        const NotificationSource& source,