Add [TypeChecking=Interface] to XSLTProcessor interface

Source/core/xml/XSLTProcessor.cpp

 /*
  * This file is part of the XSL implementation.
  *
  * Copyright (C) 2004, 2005, 2006, 2007, 2008 Apple, Inc. All rights reserved.
  * Copyright (C) 2005, 2006 Alexey Proskuryakov <ap@webkit.org>
  *
  * 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
  * version 2 of the License, or (at your option) any later version.
@@ skipping 88 matching lines @@
     DocumentEncodingData data;
     data.setEncoding(sourceEncoding.isEmpty() ? UTF8Encoding() : WTF::TextEncoding(sourceEncoding));
     result->setEncodingData(data);
     result->setContent(documentSource);
 
     return result.release();
 }
 
 PassRefPtrWillBeRawPtr<Document> XSLTProcessor::transformToDocument(Node* sourceNode)
 {
-    if (!sourceNode)
-        return nullptr;
-
     String resultMIMEType;
     String resultString;
     String resultEncoding;
     if (!transformToString(sourceNode, resultMIMEType, resultString, resultEncoding))
         return nullptr;
     return createDocumentFromSource(resultString, resultEncoding, resultMIMEType, sourceNode, 0);
 }
 
 PassRefPtrWillBeRawPtr<DocumentFragment> XSLTProcessor::transformToFragment(Node* sourceNode, Document* outputDoc)
 {
-    if (!sourceNode || !outputDoc)
-        return nullptr;
-
     String resultMIMEType;
     String resultString;
     String resultEncoding;
 
     // If the output document is HTML, default to HTML method.
     if (outputDoc->isHTMLDocument())
         resultMIMEType = "text/html";
 
     if (!transformToString(sourceNode, resultMIMEType, resultString, resultEncoding))
         return nullptr;
@@ skipping 28 matching lines @@
 }
 
 DEFINE_TRACE(XSLTProcessor)
 {
     visitor->trace(m_stylesheet);
     visitor->trace(m_stylesheetRootNode);
     visitor->trace(m_document);
 }
 
 } // namespace blink