Revert of [Oilpan] Prepare full definition of classes before using Member

third_party/WebKit/Source/core/dom/ProcessingInstruction.h

 /*
  * Copyright (C) 2000 Peter Kelly (pmk@post.com)
  * Copyright (C) 2006 Apple Inc. All rights reserved.
  *
  * 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.
  *
  * This library is distributed in the hope that it will be useful,
@@ skipping 27 matching lines @@
 public:
     static PassRefPtrWillBeRawPtr<ProcessingInstruction> create(Document&, const String& target, const String& data);
     ~ProcessingInstruction() override;
     DECLARE_VIRTUAL_TRACE();
 
     const String& target() const { return m_target; }
 
     void setCreatedByParser(bool createdByParser) { m_createdByParser = createdByParser; }
 
     const String& localHref() const { return m_localHref; }
-    StyleSheet* sheet() const;
+    StyleSheet* sheet() const { return m_sheet.get(); }
 
     bool isCSS() const { return m_isCSS; }
     bool isXSL() const { return m_isXSL; }
 
     void didAttributeChanged();
     bool isLoading() const;
 
     // For XSLT
     class DetachableEventListener : public WillBeGarbageCollectedMixin {
     public:
@@ skipping 58 matching lines @@
 DEFINE_NODE_TYPE_CASTS(ProcessingInstruction, nodeType() == Node::PROCESSING_INSTRUCTION_NODE);
 
 inline bool isXSLStyleSheet(const Node& node)
 {
     return node.nodeType() == Node::PROCESSING_INSTRUCTION_NODE && toProcessingInstruction(node).isXSL();
 }
 
 } // namespace blink
 
 #endif // ProcessingInstruction_h