Remove implementation of Panels on OSes other than ChromeOS.

chrome/browser/ui/panels/test_panel_notification_observer.h

-// 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.
-
-#ifndef CHROME_BROWSER_UI_PANELS_TEST_PANEL_NOTIFICATION_OBSERVER_H_
-#define CHROME_BROWSER_UI_PANELS_TEST_PANEL_NOTIFICATION_OBSERVER_H_
-
-#include "base/macros.h"
-#include "base/memory/ref_counted.h"
-#include "content/public/browser/notification_observer.h"
-#include "content/public/browser/notification_registrar.h"
-
-namespace content {
-class MessageLoopRunner;
-class NotificationSource;
-}
-
-// Common base class for a custom notification observer that waits
-// on a notification until an expected state is achieved.
-// Modeled after ui_test_utils notification observers, but can handle
-// more than one occurrence of the notification.
-class TestPanelNotificationObserver : public content::NotificationObserver {
- public:
-  TestPanelNotificationObserver(int notification,
-                                const content::NotificationSource& source);
-  ~TestPanelNotificationObserver() override;
-
-  // Wait until the expected state is achieved.
-  void Wait();
-
-  // content::NotificationObserver:
-  void Observe(int type,
-               const content::NotificationSource& source,
-               const content::NotificationDetails& details) override;
-
- protected:
-  virtual bool AtExpectedState() = 0;
-
-  bool seen_;  // true after transition to expected state has been seen
-  bool running_;  // indicates whether message loop is running
-  content::NotificationRegistrar registrar_;
-  scoped_refptr<content::MessageLoopRunner> message_loop_runner_;
-
-  DISALLOW_COPY_AND_ASSIGN(TestPanelNotificationObserver);
-};
-
-#endif  // CHROME_BROWSER_UI_PANELS_TEST_PANEL_NOTIFICATION_OBSERVER_H_