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

third_party/WebKit/public/web/WebPluginContainer.h

 /*
  * Copyright (C) 2009 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 86 matching lines @@
     // execution, if any.
     virtual WebString executeScriptURL(const WebURL&, bool popupsAllowed) = 0;
 
     // Loads an URL in the specified frame (or the frame containing this
     // plugin if target is empty).  If notifyNeeded is true, then upon
     // completion, WebPlugin::didFinishLoadingFrameRequest is called if the
     // load was successful or WebPlugin::didFailLoadingFrameRequest is
     // called if the load failed.  The given notifyData is passed along to
     // the callback.
     virtual void loadFrameRequest(
-        const WebURLRequest&, const WebString& target, bool notifyNeeded, void* notifyData) = 0;
+        const WebURLRequest&, const WebString& target) = 0;
 
     // Determines whether the given rectangle in this plugin is above all other
     // content. The rectangle is in the plugin's coordinate system.
     virtual bool isRectTopmost(const WebRect&) = 0;
 
     // Notifies when the plugin changes the kind of touch-events it accepts.
     virtual void requestTouchEventType(TouchEventRequestType) = 0;
 
     // Notifies when the plugin starts/stops accepting wheel events. Without
     // calling the function with true, the container might not always able to
@@ skipping 18 matching lines @@
     // WebPluginContainer does *not* take ownership.
     virtual void setWebLayer(WebLayer*) = 0;
 
 protected:
     ~WebPluginContainer() { }
 };
 
 } // namespace blink
 
 #endif