[Oilpan] Prepare full definition of classes before using Member

third_party/WebKit/Source/platform/mhtml/MHTMLArchive.h

 /*
  * Copyright (C) 2011 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 80 matching lines @@
         SharedBuffer& outputBuffer);
 
     // Generates and returns a full MHTML document.
     static PassRefPtr<SharedBuffer> generateMHTMLData(
         const Vector<SerializedResource>&, EncodingPolicy,
         const String& title, const String& mimeType);
 
     typedef WillBeHeapVector<RefPtrWillBeMember<ArchiveResource>> SubArchiveResources;
     typedef WillBeHeapVector<RefPtrWillBeMember<MHTMLArchive>> SubFrameArchives;
 
-    ArchiveResource* mainResource() { return m_mainResource.get(); }
+    ArchiveResource* mainResource() const;
     const SubArchiveResources& subresources() const { return m_subresources; }
     const SubFrameArchives& subframeArchives() const { return m_subframeArchives; }
 
     DECLARE_TRACE();
 
 private:
     friend class MHTMLParser;
     MHTMLArchive();
 
     void setMainResource(PassRefPtrWillBeRawPtr<ArchiveResource>);
     void addSubresource(PassRefPtrWillBeRawPtr<ArchiveResource>);
     void addSubframeArchive(PassRefPtrWillBeRawPtr<MHTMLArchive>);
 
 #if !ENABLE(OILPAN)
     void clearAllSubframeArchives();
     void clearAllSubframeArchivesImpl(SubFrameArchives* clearedArchives);
 #endif
 
     RefPtrWillBeMember<ArchiveResource> m_mainResource;
     SubArchiveResources m_subresources;
     SubFrameArchives m_subframeArchives;
 };
 
 }
 
 #endif