Clean up forward declarations in WebKit/Source

Source/core/xml/DocumentXSLT.h

 // Copyright 2014 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 DocumentXSLT_h
 #define DocumentXSLT_h
 
 #include "core/dom/DocumentSupplementable.h"
 #include "platform/heap/Handle.h"
 #include "wtf/RefPtr.h"
 
 namespace blink {
 
 class Document;
-class EventListener;
-class ExecutionContext;
 class ProcessingInstruction;
 
 class DocumentXSLT final : public NoBaseWillBeGarbageCollected<DocumentXSLT>, public DocumentSupplement {
     WTF_MAKE_NONCOPYABLE(DocumentXSLT);
     WILL_BE_USING_GARBAGE_COLLECTED_MIXIN(DocumentXSLT);
 public:
     Document* transformSourceDocument()
     {
         return m_transformSourceDocument.get();
     }
@@ skipping 20 matching lines @@
 
 private:
     DocumentXSLT();
 
     RefPtrWillBeMember<Document> m_transformSourceDocument;
 };
 
 } // namespace blink
 
 #endif