Consistently use ElementTraversal API when looking for an Element

Source/core/html/HTMLAppletElement.cpp

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  *           (C) 2000 Stefan Schimanski (1Stein@gmx.de)
  * Copyright (C) 2004, 2005, 2006, 2008, 2009, 2012 Apple Inc. All rights reserved.
  * Copyright (C) 2008 Nokia Corporation and/or its subsidiary(-ies)
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
  * License as published by the Free Software Foundation; either
@@ skipping 154 matching lines @@
     paramNames.append("baseURL");
     KURL baseURL = document().baseURL();
     paramValues.append(baseURL.string());
 
     const AtomicString& mayScript = getAttribute(mayscriptAttr);
     if (!mayScript.isNull()) {
         paramNames.append("mayScript");
         paramValues.append(mayScript.string());
     }
 
-    for (Node* child = firstChild(); child; child = child->nextSibling()) {
+    for (Element* child = ElementTraversal::firstWithin(*this); child; child = ElementTraversal::nextSibling(*child)) {
         if (!child->hasTagName(paramTag))
             continue;
 
         HTMLParamElement* param = toHTMLParamElement(child);
         if (param->name().isEmpty())
             continue;
 
         paramNames.append(param->name());
         paramValues.append(param->value());
     }
@@ skipping 37 matching lines @@
 
     if (!document().contentSecurityPolicy()->allowObjectFromSource(url)
         || !document().contentSecurityPolicy()->allowPluginType(appletMimeType, appletMimeType, url)) {
         renderEmbeddedObject()->setPluginUnavailabilityReason(RenderEmbeddedObject::PluginBlockedByContentSecurityPolicy);
         return false;
     }
     return true;
 }
 
 }