Move enable extensions define to a build flag.

chrome/browser/notifications/platform_notification_service_impl.cc

Index: chrome/browser/notifications/platform_notification_service_impl.cc
diff --git a/chrome/browser/notifications/platform_notification_service_impl.cc b/chrome/browser/notifications/platform_notification_service_impl.cc
index aa0683afd4a9f85362153789b7c45c744de4ca91..2f79b35ba28726a7a4df6c89f2a6657713a91913 100644
--- a/chrome/browser/notifications/platform_notification_service_impl.cc
+++ b/chrome/browser/notifications/platform_notification_service_impl.cc
@@ -35,6 +35,7 @@
 #include "content/public/browser/user_metrics.h"
 #include "content/public/common/notification_resources.h"
 #include "content/public/common/platform_notification_data.h"
+#include "extensions/features/features.h"
 #include "ui/base/l10n/l10n_util.h"
 #include "ui/base/resource/resource_bundle.h"
 #include "ui/message_center/notification.h"
@@ -47,7 +48,7 @@
 #include "chrome/browser/lifetime/scoped_keep_alive.h"
 #endif
 
-#if defined(ENABLE_EXTENSIONS)
+#if BUILDFLAG(ENABLE_EXTENSIONS)
 #include "chrome/browser/notifications/notifier_state_tracker.h"
 #include "chrome/browser/notifications/notifier_state_tracker_factory.h"
 #include "extensions/browser/extension_registry.h"
@@ -183,7 +184,7 @@ PlatformNotificationServiceImpl::CheckPermissionOnUIThread(
   Profile* profile = Profile::FromBrowserContext(browser_context);
   DCHECK(profile);
 
-#if defined(ENABLE_EXTENSIONS)
+#if BUILDFLAG(ENABLE_EXTENSIONS)
   // Extensions support an API permission named "notification". This will grant
   // not only grant permission for using the Chrome App extension API, but also
   // for the Web Notification API.
@@ -224,7 +225,7 @@ PlatformNotificationServiceImpl::CheckPermissionOnIOThread(
   DCHECK_CURRENTLY_ON(BrowserThread::IO);
 
   ProfileIOData* io_data = ProfileIOData::FromResourceContext(resource_context);
-#if defined(ENABLE_EXTENSIONS)
+#if BUILDFLAG(ENABLE_EXTENSIONS)
   // Extensions support an API permission named "notification". This will grant
   // not only grant permission for using the Chrome App extension API, but also
   // for the Web Notification API.
@@ -484,7 +485,7 @@ PlatformNotificationServiceImpl::GetNotificationDisplayService(
 base::string16 PlatformNotificationServiceImpl::DisplayNameForContextMessage(
     Profile* profile,
     const GURL& origin) const {
-#if defined(ENABLE_EXTENSIONS)
+#if BUILDFLAG(ENABLE_EXTENSIONS)
   // If the source is an extension, lookup the display name.
   if (origin.SchemeIs(extensions::kExtensionScheme)) {
     const extensions::Extension* extension =