Remove the OnError method from notification delegates.

content/public/browser/desktop_notification_delegate.h

Index: content/public/browser/desktop_notification_delegate.h
diff --git a/content/public/browser/desktop_notification_delegate.h b/content/public/browser/desktop_notification_delegate.h
index 27c5fd7f28c08423b4e96d8560e411c3ad4551f6..aaf2c9d98d722e0b34e1cb2557012066a1d44f0f 100644
--- a/content/public/browser/desktop_notification_delegate.h
+++ b/content/public/browser/desktop_notification_delegate.h
@@ -16,9 +16,6 @@ class DesktopNotificationDelegate {
   // The notification was shown.
   virtual void NotificationDisplayed() = 0;
 
-  // The notification couldn't be shown due to an error.
-  virtual void NotificationError() = 0;
-
   // The notification was closed.
   virtual void NotificationClosed(bool by_user) = 0;