Remove the OnError method from notification delegates.

chrome/browser/extensions/api/notifications/notifications_api.cc

 // Copyright (c) 2012 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.
 
 #include "chrome/browser/extensions/api/notifications/notifications_api.h"
 
 #include "base/callback.h"
 #include "base/guid.h"
 #include "base/rand_util.h"
 #include "base/strings/string_number_conversions.h"
@@ skipping 69 matching lines @@
       : api_function_(api_function),
         profile_(profile),
         extension_id_(extension_id),
         id_(id),
         scoped_id_(CreateScopedIdentifier(extension_id, id)) {
     DCHECK(api_function_.get());
   }
 
   void Display() override {}
 
-  void Error() override {}
-
   void Close(bool by_user) override {
     EventRouter::UserGestureState gesture =
         by_user ? EventRouter::USER_GESTURE_ENABLED
                 : EventRouter::USER_GESTURE_NOT_ENABLED;
     scoped_ptr<base::ListValue> args(CreateBaseEventArgs());
     args->Append(new base::FundamentalValue(by_user));
     SendEvent(notifications::OnClosed::kEventName, gesture, args.Pass());
   }
 
   void Click() override {
@@ skipping 503 matching lines @@
           ? api::notifications::PERMISSION_LEVEL_GRANTED
           : api::notifications::PERMISSION_LEVEL_DENIED;
 
   SetResult(new base::StringValue(api::notifications::ToString(result)));
   SendResponse(true);
 
   return true;
 }
 
 }  // namespace extensions