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

content/renderer/pepper/pepper_webplugin_impl.h

Index: content/renderer/pepper/pepper_webplugin_impl.h
diff --git a/content/renderer/pepper/pepper_webplugin_impl.h b/content/renderer/pepper/pepper_webplugin_impl.h
index 8371eb05c0ec01fbc24c0bebddeffc8f828de471..c0685cc66482a96646da8b101a55b0cf3f6c002c 100644
--- a/content/renderer/pepper/pepper_webplugin_impl.h
+++ b/content/renderer/pepper/pepper_webplugin_impl.h
@@ -61,11 +61,6 @@ class PepperWebPluginImpl : public blink::WebPlugin {
   void didReceiveData(const char* data, int data_length) override;
   void didFinishLoading() override;
   void didFailLoading(const blink::WebURLError&) override;
-  void didFinishLoadingFrameRequest(const blink::WebURL& url,
-                                    void* notify_data) override;
-  void didFailLoadingFrameRequest(const blink::WebURL& url,
-                                  void* notify_data,
-                                  const blink::WebURLError& error) override;
   bool hasSelection() const override;
   blink::WebString selectionAsText() const override;
   blink::WebString selectionAsMarkup() const override;