Fix panel showing logic when Chrome enters the fullscreen mode

chrome/browser/ui/panels/display_settings_provider.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_DISPLAY_SETTINGS_PROVIDER_H_
 #define CHROME_BROWSER_UI_PANELS_DISPLAY_SETTINGS_PROVIDER_H_
 
 #include "base/observer_list.h"
 #include "base/timer.h"
 #include "ui/gfx/rect.h"
@@ skipping 110 matching lines @@
 
   bool is_full_screen() const { return is_full_screen_; }
 
  protected:
   DisplaySettingsProvider();
 
   // Returns true if we need to perform fullscreen check periodically.
   virtual bool NeedsPeriodicFullScreenCheck() const;
 
   // Returns true if full screen or presentation mode in main screen is entered.
-  virtual bool IsFullScreen() const;
+  virtual bool IsFullScreen();
 
   // Callback to perform periodic check for full screen mode changes.
   void CheckFullScreenMode();
 
  private:
   // Observers that listen to various display settings changes.
   ObserverList<DisplayObserver> display_observers_;
   ObserverList<DesktopBarObserver> desktop_bar_observers_;
   ObserverList<FullScreenObserver> full_screen_observers_;
 
   // True if full screen mode or presentation mode is entered.
   bool is_full_screen_;
 
   // Timer used to detect full-screen mode change.
   base::RepeatingTimer<DisplaySettingsProvider> full_screen_mode_timer_;
 
   DISALLOW_COPY_AND_ASSIGN(DisplaySettingsProvider);
 };
 
 #endif  // CHROME_BROWSER_UI_PANELS_DISPLAY_SETTINGS_PROVIDER_H_