Some random Web Notification cleanups

Source/modules/notifications/NotificationPermissionClient.cpp

Index: Source/modules/notifications/NotificationPermissionClient.cpp
diff --git a/Source/modules/notifications/NotificationPermissionClient.cpp b/Source/modules/notifications/NotificationPermissionClient.cpp
index da8966e3cacc55a8986771f58252916549db23f2..e721abdd8d07db2f369e2bda832239ec94dafa90 100644
--- a/Source/modules/notifications/NotificationPermissionClient.cpp
+++ b/Source/modules/notifications/NotificationPermissionClient.cpp
@@ -19,11 +19,11 @@ const char* NotificationPermissionClient::supplementName()
 NotificationPermissionClient* NotificationPermissionClient::from(ExecutionContext* context)
 {
     if (!context->isDocument())
-        return 0;
+        return nullptr;
 
     const Document* document = toDocument(context);
     if (!document->frame() || !document->frame()->isLocalFrame())
-        return 0;
+        return nullptr;
 
     return static_cast<NotificationPermissionClient*>(WillBeHeapSupplement<LocalFrame>::from(document->frame(), supplementName()));
 }