RootWindowController::GetFullscreenWindow() should return the active one.

chrome/browser/fullscreen_win.cc

 // Copyright (c) 2011 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/fullscreen.h"
 
 #include <windows.h>
 #include <shellapi.h>
 
 #include "base/logging.h"
@@ skipping 88 matching lines @@
   ::FreeConsole();
 
   return (modes & (CONSOLE_FULLSCREEN | CONSOLE_FULLSCREEN_HARDWARE)) != 0;
 }
 
 bool IsFullScreenMode() {
 #if defined(USE_ASH)
   if (chrome::GetActiveDesktop() == chrome::HOST_DESKTOP_TYPE_ASH) {
     ash::internal::RootWindowController* controller =
         ash::internal::RootWindowController::ForActiveRootWindow();
-    return controller && controller->GetFullscreenWindow();
+    return controller && controller->GetTopmostFullscreenWindow();
   }
 #endif
   return IsPlatformFullScreenMode() ||
          IsFullScreenWindowMode() ||
          IsFullScreenConsoleMode();
 }