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

content/renderer/render_frame_impl.h

 // Copyright 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef CONTENT_RENDERER_RENDER_FRAME_IMPL_H_
 #define CONTENT_RENDERER_RENDER_FRAME_IMPL_H_
 
 #include <string>
 #include <vector>
 
@@ skipping 513 matching lines @@
       const blink::WebURL& url,
       const blink::WebCString& security_info,
       const blink::WebURL& main_resource_url,
       const blink::WebCString& main_resource_security_info) override;
   void didRunContentWithCertificateErrors(
       const blink::WebURL& url,
       const blink::WebCString& security_info,
       const blink::WebURL& main_resource_url,
       const blink::WebCString& main_resource_security_info) override;
   void didChangePerformanceTiming() override;
-  void didAbortLoading(blink::WebLocalFrame* frame) override;
   void didCreateScriptContext(blink::WebLocalFrame* frame,
                               v8::Local<v8::Context> context,
                               int extension_group,
                               int world_id) override;
   void willReleaseScriptContext(blink::WebLocalFrame* frame,
                                 v8::Local<v8::Context> context,
                                 int world_id) override;
   void didChangeScrollOffset(blink::WebLocalFrame* frame) override;
   void willInsertBody(blink::WebLocalFrame* frame) override;
   void reportFindInPageMatchCount(int request_id,
@@ skipping 577 matching lines @@
 #endif
 
   base::WeakPtrFactory<RenderFrameImpl> weak_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(RenderFrameImpl);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_RENDERER_RENDER_FRAME_IMPL_H_