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

third_party/WebKit/Source/core/loader/FrameLoaderClient.h

 /*
  * Copyright (C) 2006, 2007, 2008, 2009, 2010, 2011, 2012 Apple Inc. All rights reserved.
  * Copyright (C) 2012 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 206 matching lines @@
     virtual PassOwnPtr<WebServiceWorkerProvider> createServiceWorkerProvider() = 0;
 
     virtual bool isControlledByServiceWorker(DocumentLoader&) = 0;
 
     virtual int64_t serviceWorkerID(DocumentLoader&) = 0;
 
     virtual SharedWorkerRepositoryClient* sharedWorkerRepositoryClient() { return 0; }
 
     virtual PassOwnPtr<WebApplicationCacheHost> createApplicationCacheHost(WebApplicationCacheHostClient*) = 0;
 
-    virtual void didStopAllLoaders() { }
-
     virtual void dispatchDidChangeManifest() { }
 
     virtual unsigned backForwardLength() { return 0; }
 
     virtual bool isFrameLoaderClientImpl() const { return false; }
 
     // Called when elements preventing the sudden termination of the frame
     // become present or stop being present. |type| is the type of element
     // (BeforeUnload handler, Unload handler).
     enum SuddenTerminationDisablerType {
         BeforeUnloadHandler,
         UnloadHandler,
     };
     virtual void suddenTerminationDisablerChanged(bool present, SuddenTerminationDisablerType) { }
 
 };
 
 } // namespace blink
 
 #endif // FrameLoaderClient_h