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

content/renderer/browser_plugin/browser_plugin.cc

Index: content/renderer/browser_plugin/browser_plugin.cc
diff --git a/content/renderer/browser_plugin/browser_plugin.cc b/content/renderer/browser_plugin/browser_plugin.cc
index f4b24e1cb029c0954634918d1db1fc3a77fe9973..a6b031c6aa6bbb181fe50918d9ce6dad2fae4459 100644
--- a/content/renderer/browser_plugin/browser_plugin.cc
+++ b/content/renderer/browser_plugin/browser_plugin.cc
@@ -573,16 +573,6 @@ void BrowserPlugin::didFinishLoading() {
 void BrowserPlugin::didFailLoading(const blink::WebURLError& error) {
 }
 
-void BrowserPlugin::didFinishLoadingFrameRequest(const blink::WebURL& url,
-                                                 void* notify_data) {
-}
-
-void BrowserPlugin::didFailLoadingFrameRequest(
-    const blink::WebURL& url,
-    void* notify_data,
-    const blink::WebURLError& error) {
-}
-
 bool BrowserPlugin::executeEditCommand(const blink::WebString& name) {
   BrowserPluginManager::Get()->Send(new BrowserPluginHostMsg_ExecuteEditCommand(
       browser_plugin_instance_id_,