Make multipart image documents work again.

Source/core/loader/DocumentLoader.h

 /*
  * Copyright (C) 2006, 2007, 2008, 2009 Apple Inc. All rights reserved.
  * 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:
  *
  * 1.  Redistributions of source code must retain the above copyright
  *     notice, this list of conditions and the following disclaimer.
@@ skipping 119 matching lines @@
             InitialScrollState()
                 : didRestoreFromHistory(false)
             {
             }
 
             // TODO(skobes): Move FrameView::m_wasScrolledByUser into here.
             bool didRestoreFromHistory;
         };
         InitialScrollState& initialScrollState() { return m_initialScrollState; }
 
+        bool loadingMultipartContent() const;
+
     protected:
         DocumentLoader(LocalFrame*, const ResourceRequest&, const SubstituteData&);
 
         Vector<KURL> m_redirectChain;
 
     private:
         static PassRefPtrWillBeRawPtr<DocumentWriter> createWriterFor(const Document* ownerDocument, const DocumentInit&, const AtomicString& mimeType, const AtomicString& encoding, bool dispatch, ParserSynchronizationPolicy);
 
         void ensureWriter(const AtomicString& mimeType, const KURL& overridingURL = KURL());
         void endWriting(DocumentWriter*);
@@ skipping 66 matching lines @@
         friend class ApplicationCacheHost;  // for substitute resource delivery
         OwnPtrWillBePersistent<ApplicationCacheHost> m_applicationCacheHost;
 
         RefPtr<ContentSecurityPolicy> m_contentSecurityPolicy;
         ClientHintsPreferences m_clientHintsPreferences;
         InitialScrollState m_initialScrollState;
     };
 }
 
 #endif // DocumentLoader_h