Use and add layout tests for BCP 47 language tag syntax validation.

Source/modules/notifications/Notification.cpp

 /*
  * Copyright (C) 2013 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 78 matching lines @@
     if (options.hasData()) {
         data = SerializedScriptValueFactory::instance().create(options.data(), nullptr, exceptionState, options.data().isolate());
         if (exceptionState.hadException())
             return nullptr;
     }
 
     Notification* notification = new Notification(title, context);
 
     notification->setBody(options.body());
     notification->setTag(options.tag());
-    notification->setLang(options.lang());
+
+    if (Platform::current()->isValidLocaleSyntax(options.lang()))
+        notification->setLang(options.lang());
+
     notification->setDir(options.dir());
     notification->setVibrate(NavigatorVibration::sanitizeVibrationPattern(options.vibrate()));
     notification->setSilent(options.silent());
     notification->setSerializedData(data.release());
     if (options.hasIcon()) {
         KURL iconUrl = options.icon().isEmpty() ? KURL() : context->completeURL(options.icon());
         if (!iconUrl.isEmpty() && iconUrl.isValid())
             notification->setIconUrl(iconUrl);
     }
 
@@ skipping 217 matching lines @@
     return ScriptValue(scriptState, m_serializedData->deserialize(scriptState->isolate()));
 }
 
 DEFINE_TRACE(Notification)
 {
     RefCountedGarbageCollectedEventTargetWithInlineData<Notification>::trace(visitor);
     ActiveDOMObject::trace(visitor);
 }
 
 } // namespace blink