Remove NOTIFICATION_EXTENSION_ENABLED.

extensions/browser/event_router.h

Index: extensions/browser/event_router.h
diff --git a/extensions/browser/event_router.h b/extensions/browser/event_router.h
index 48bc266980cce4ce121f64a3402d8afbc5926e8a..0f692a1012578b809b7e7e97c74fb710cfe9e0be 100644
--- a/extensions/browser/event_router.h
+++ b/extensions/browser/event_router.h
@@ -18,8 +18,6 @@
 #include "base/scoped_observer.h"
 #include "base/values.h"
 #include "components/keyed_service/core/keyed_service.h"
-#include "content/public/browser/notification_observer.h"
-#include "content/public/browser/notification_registrar.h"
 #include "content/public/browser/render_process_host_observer.h"
 #include "extensions/browser/event_listener_map.h"
 #include "extensions/browser/extension_event_histogram_value.h"
@@ -45,7 +43,6 @@ struct Event;
 struct EventListenerInfo;
 
 class EventRouter : public KeyedService,
-                    public content::NotificationObserver,
                     public ExtensionRegistryObserver,
                     public EventListenerMap::Delegate,
                     public content::RenderProcessHostObserver {
@@ -227,9 +224,6 @@ class EventRouter : public KeyedService,
   void SetRegisteredEvents(const std::string& extension_id,
                            const std::set<std::string>& events);
 
-  void Observe(int type,
-               const content::NotificationSource& source,
-               const content::NotificationDetails& details) override;
   // ExtensionRegistryObserver implementation.
   void OnExtensionLoaded(content::BrowserContext* browser_context,
                          const Extension* extension) override;
@@ -327,8 +321,6 @@ class EventRouter : public KeyedService,
   // tests.
   ExtensionPrefs* extension_prefs_;
 
-  content::NotificationRegistrar registrar_;
-
   ScopedObserver<ExtensionRegistry, ExtensionRegistryObserver>
       extension_registry_observer_;