Some random Web Notification cleanups

Source/modules/notifications/NotificationData.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 NotificationData_h
 #define NotificationData_h
 
 #include "modules/ModulesExport.h"
 #include "public/platform/modules/notifications/WebNotificationData.h"
-#include "wtf/text/WTFString.h"
+
+namespace WTF {
+class String;
+}
 
 namespace blink {
 
 class ExceptionState;
 class ExecutionContext;
 class NotificationOptions;
 
 // Creates a WebNotificationData object based on the developer-provided notification data. When the
 // data is deemed invalid, an exception will be thrown to the passed exception state.
 MODULES_EXPORT WebNotificationData createWebNotificationData(ExecutionContext*, const String& title, const NotificationOptions&, ExceptionState&);
 
 } // namespace blink
 
 #endif // NotificationData_h