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

ash/root_window_controller.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 ASH_ROOT_WINDOW_CONTROLLER_H_
 #define ASH_ROOT_WINDOW_CONTROLLER_H_
 
 #include <map>
 
 #include "ash/ash_export.h"
@@ skipping 188 matching lines @@
 
   // Moves child windows to |dest|.
   void MoveWindowsTo(aura::RootWindow* dest);
 
   // Force the shelf to query for it's current visibility state.
   void UpdateShelfVisibility();
 
   // Initialize touch HUDs if necessary.
   void InitTouchHuds();
 
-  // Returns the window, if any, which is in fullscreen mode in the active
-  // workspace. Exposed here so clients of Ash don't need to know the details
-  // of workspace management.
-  const aura::Window* GetFullscreenWindow() const;
+  // Returns the window, if any, which is in fullscreen mode. If multiple
+  // windows are in fullscreen state, the topmost one is preferred.
+  const aura::Window* GetTopmostFullscreenWindow() const;
 
  private:
   void InitLayoutManagers();
 
   // Initializes |system_background_| and possibly also |boot_splash_screen_|.
   // |is_first_run_after_boot| determines the background's initial color.
   void CreateSystemBackground(bool is_first_run_after_boot);
 
   // Creates each of the special window containers that holds windows of various
   // types in the shell UI.
@@ skipping 61 matching lines @@
   scoped_ptr<AnimatingDesktopController> animating_wallpaper_controller_;
   scoped_ptr<views::corewm::ScopedCaptureClient> capture_client_;
 
   DISALLOW_COPY_AND_ASSIGN(RootWindowController);
 };
 
 }  // namespace internal
 }  // ash
 
 #endif  //  ASH_ROOT_WINDOW_CONTROLLER_H_