Move enable extensions define to a build flag.

chrome/browser/notifications/notifier_state_tracker.h

 // Copyright 2015 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_NOTIFICATIONS_NOTIFIER_STATE_TRACKER_H_
 #define CHROME_BROWSER_NOTIFICATIONS_NOTIFIER_STATE_TRACKER_H_
 
 #include <set>
 #include <string>
 
 #include "base/macros.h"
 #include "components/keyed_service/core/keyed_service.h"
 #include "components/prefs/pref_member.h"
+#include "extensions/features/features.h"
 
-#if defined(ENABLE_EXTENSIONS)
+#if BUILDFLAG(ENABLE_EXTENSIONS)
 #include "base/scoped_observer.h"
 #include "extensions/browser/extension_registry.h"
 #include "extensions/browser/extension_registry_observer.h"
 #endif
 
 class Profile;
 
 namespace message_center {
 struct NotifierId;
 }
 
 namespace user_prefs {
 class PrefRegistrySyncable;
 }
 
 // Tracks whether a given NotifierId can send notifications.
 class NotifierStateTracker : public KeyedService
-#if defined(ENABLE_EXTENSIONS)
+#if BUILDFLAG(ENABLE_EXTENSIONS)
                            , public extensions::ExtensionRegistryObserver
 #endif
                                {
  public:
   // Register profile-specific prefs of notifications.
   static void RegisterProfilePrefs(user_prefs::PrefRegistrySyncable* prefs);
 
   explicit NotifierStateTracker(Profile* profile);
   ~NotifierStateTracker() override;
 
   // Returns whether the notifier with |notifier_id| may send notifications.
   bool IsNotifierEnabled(const message_center::NotifierId& notifier_id) const;
 
   // Updates whether the notifier with |notifier_id| may send notifications.
   void SetNotifierEnabled(const message_center::NotifierId& notifier_id,
                           bool enabled);
 
  private:
   // Called when the string list pref has been changed.
   void OnStringListPrefChanged(
       const char* pref_name, std::set<std::string>* ids_field);
 
-#if defined(ENABLE_EXTENSIONS)
+#if BUILDFLAG(ENABLE_EXTENSIONS)
   // Fires a permission-level change event when an extension notifier has had
   // their notification permission changed.
   void FirePermissionLevelChangedEvent(
       const message_center::NotifierId& notifier_id,
       bool enabled);
 
   // extensions::ExtensionRegistryObserver:
   void OnExtensionUninstalled(content::BrowserContext* browser_context,
                               const extensions::Extension* extension,
                               extensions::UninstallReason reason) override;
 #endif
 
   // The profile which owns this object.
   Profile* profile_;
 
   // Prefs listener for disabled_extension_id.
   StringListPrefMember disabled_extension_id_pref_;
 
   // Prefs listener for disabled_system_component_id.
   StringListPrefMember disabled_system_component_id_pref_;
 
   // On-memory data for the availability of extensions.
   std::set<std::string> disabled_extension_ids_;
 
   // On-memory data for the availability of system_component.
   std::set<std::string> disabled_system_component_ids_;
 
-#if defined(ENABLE_EXTENSIONS)
+#if BUILDFLAG(ENABLE_EXTENSIONS)
   // An observer to listen when extension is uninstalled.
   ScopedObserver<extensions::ExtensionRegistry,
                  extensions::ExtensionRegistryObserver>
       extension_registry_observer_;
 #endif
 
   DISALLOW_COPY_AND_ASSIGN(NotifierStateTracker);
 };
 
 #endif  // CHROME_BROWSER_NOTIFICATIONS_NOTIFIER_STATE_TRACKER_H_