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

third_party/WebKit/public/web/WebPlugin.h

 /*
  * Copyright (C) 2009, 2012 Google Inc. All rights reserved.
  * Copyright (C) 2014 Opera Software ASA. 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.
@@ skipping 100 matching lines @@
     virtual bool acceptsInputEvents() = 0;
     virtual WebInputEventResult handleInputEvent(const WebInputEvent&, WebCursorInfo&) = 0;
 
     virtual bool handleDragStatusUpdate(WebDragStatus, const WebDragData&, WebDragOperationsMask, const WebPoint& position, const WebPoint& screenPosition) { return false; }
 
     virtual void didReceiveResponse(const WebURLResponse&) = 0;
     virtual void didReceiveData(const char* data, int dataLength) = 0;
     virtual void didFinishLoading() = 0;
     virtual void didFailLoading(const WebURLError&) = 0;
 
-    // Called in response to WebPluginContainer::loadFrameRequest
-    virtual void didFinishLoadingFrameRequest(
-        const WebURL&, void* notifyData) = 0;
-    virtual void didFailLoadingFrameRequest(
-        const WebURL&, void* notifyData, const WebURLError&) = 0;
-
     // Printing interface.
     // Whether the plugin supports its own paginated print. The other print
     // interface methods are called only if this method returns true.
     virtual bool supportsPaginatedPrint() { return false; }
     // Returns true if the printed content should not be scaled to
     // the printer's printable area.
     virtual bool isPrintScalingDisabled() { return false; }
     // Returns true on success and sets the out parameter to the print preset options for the document.
     virtual bool getPrintPresetOptionsFromDocument(WebPrintPresetOptions*) { return false; }
 
@@ skipping 49 matching lines @@
 
     virtual bool isPlaceholder() { return true; }
 
 protected:
     ~WebPlugin() { }
 };
 
 } // namespace blink
 
 #endif