Provide default implementations for NotificationDelegate methods.

chrome/browser/status_icons/desktop_notification_balloon.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/status_icons/desktop_notification_balloon.h"
 
 #include "base/bind.h"
 #include "base/strings/string_number_conversions.h"
 #include "base/threading/thread_restrictions.h"
 #include "chrome/browser/browser_process.h"
@@ skipping 27 matching lines @@
   explicit DummyNotificationDelegate(const std::string& id, Profile* profile)
       : id_(kNotificationPrefix + id), profile_(profile) {}
 
   void Display() override {
     base::MessageLoop::current()->PostDelayedTask(
         FROM_HERE,
         base::Bind(
             &CloseBalloon, id(), NotificationUIManager::GetProfileID(profile_)),
         base::TimeDelta::FromSeconds(kTimeoutSeconds));
   }
-  void Error() override {}
-  void Close(bool by_user) override {}
-  void Click() override {}
   std::string id() const override { return id_; }
 
  private:
   ~DummyNotificationDelegate() override {}
 
   std::string id_;
   Profile* profile_;
 };
 
 }  // anonymous namespace
@@ skipping 24 matching lines @@
   notification_id_ = DesktopNotificationService::AddIconNotification(
       GURL(),
       title,
       contents,
       gfx::Image(icon),
       base::string16(),
       new DummyNotificationDelegate(base::IntToString(id_count_++), profile_),
       profile);
   profile_ = profile;
 }