Fix panel showing logic when Chrome enters the fullscreen mode

chrome/browser/ui/panels/display_settings_provider.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/ui/panels/display_settings_provider.h"
 
 #include "base/logging.h"
 #include "chrome/browser/fullscreen.h"
 #include "ui/gfx/screen.h"
 
@@ skipping 23 matching lines @@
   desktop_bar_observers_.AddObserver(observer);
 }
 
 void DisplaySettingsProvider::RemoveDesktopBarObserver(
     DesktopBarObserver* observer) {
   desktop_bar_observers_.RemoveObserver(observer);
 }
 
 void DisplaySettingsProvider::AddFullScreenObserver(
     FullScreenObserver* observer) {
+  is_full_screen_ = IsFullScreen();
   full_screen_observers_.AddObserver(observer);
 
   if (full_screen_observers_.size() == 1 && NeedsPeriodicFullScreenCheck()) {
     full_screen_mode_timer_.Start(FROM_HERE,
         base::TimeDelta::FromMilliseconds(kFullScreenModeCheckIntervalMs),
         this, &DisplaySettingsProvider::CheckFullScreenMode);
   }
 }
 
 void DisplaySettingsProvider::RemoveFullScreenObserver(
@@ skipping 76 matching lines @@
   bool is_full_screen = IsFullScreen();
   if (is_full_screen == is_full_screen_)
     return;
   is_full_screen_ = is_full_screen;
 
   FOR_EACH_OBSERVER(FullScreenObserver,
                     full_screen_observers_,
                     OnFullScreenModeChanged(is_full_screen_));
 }
 
-bool DisplaySettingsProvider::IsFullScreen() const {
+bool DisplaySettingsProvider::IsFullScreen() {
   return IsFullScreenMode();
 }
 
 #if defined(USE_AURA)
 // static
 DisplaySettingsProvider* DisplaySettingsProvider::Create() {
   return new DisplaySettingsProvider();
 }
 #endif