Emit error events if the loading of an object element failed

components/plugins/renderer/webview_plugin.h

Index: components/plugins/renderer/webview_plugin.h
diff --git a/components/plugins/renderer/webview_plugin.h b/components/plugins/renderer/webview_plugin.h
index 7f4ad1045a850bad918d6c85c898a0247a61a71a..f907f5e0fab7aabc117d2368880d7dbdd3dbf8cd 100644
--- a/components/plugins/renderer/webview_plugin.h
+++ b/components/plugins/renderer/webview_plugin.h
@@ -55,6 +55,8 @@ class WebViewPlugin : public blink::WebPlugin,
 
     // Called when the unobscured rect of the plugin is updated.
     virtual void OnUnobscuredRectUpdate(const gfx::Rect& unobscured_rect) {}
+
+    virtual bool IsErrorPlaceholder() = 0;
   };
 
   // Convenience method to set up a new WebViewPlugin using |preferences|
@@ -84,6 +86,8 @@ class WebViewPlugin : public blink::WebPlugin,
 
   v8::Local<v8::Object> v8ScriptableObject(v8::Isolate* isolate) override;
 
+  bool isErrorPlaceholder() override;
+
   void updateAllLifecyclePhases() override;
   void paint(blink::WebCanvas* canvas, const blink::WebRect& rect) override;