Remove PluginLoadObserver and related logic, it was only used for NPAPI.

third_party/WebKit/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 80 matching lines @@
     const KURL& unreachableURL() const;
     const KURL& urlForHistory() const;
 
     const AtomicString& responseMIMEType() const;
 
     void didChangePerformanceTiming();
     void updateForSameDocumentNavigation(const KURL&, SameDocumentNavigationSource);
     void stopLoading();
     bool isLoading() const;
     const ResourceResponse& response() const { return m_response; }
-    const ResourceError& mainDocumentError() const { return m_mainDocumentError; }
     bool isClientRedirect() const { return m_isClientRedirect; }
     void setIsClientRedirect(bool isClientRedirect) { m_isClientRedirect = isClientRedirect; }
     bool replacesCurrentHistoryItem() const { return m_replacesCurrentHistoryItem; }
     void setReplacesCurrentHistoryItem(bool replacesCurrentHistoryItem) { m_replacesCurrentHistoryItem = replacesCurrentHistoryItem; }
 
     bool isCommittedButEmpty() const { return m_state == Committed; }
 
     void setSentDidFinishLoad() { m_state = SentDidFinishLoad; }
     bool sentDidFinishLoad() const { return m_state == SentDidFinishLoad; }
 
@@ skipping 94 matching lines @@
 
     SubstituteData m_substituteData;
 
     // The 'working' request. It may be mutated
     // several times from the original request to include additional
     // headers, cookie information, canonicalization and redirects.
     ResourceRequest m_request;
 
     ResourceResponse m_response;
 
-    ResourceError m_mainDocumentError;
-
     bool m_isClientRedirect;
     bool m_replacesCurrentHistoryItem;
 
     NavigationType m_navigationType;
 
     RefPtrWillBeMember<MHTMLArchive> m_archive;
 
     DocumentLoadTiming m_documentLoadTiming;
 
     double m_timeOfLastDataReceived;
@@ skipping 17 matching lines @@
     // Used to protect against reentrancy into dataReceived().
     bool m_inDataReceived;
     RefPtr<SharedBuffer> m_dataBuffer;
 };
 
 DECLARE_WEAK_IDENTIFIER_MAP(DocumentLoader);
 
 } // namespace blink
 
 #endif // DocumentLoader_h