Show overview mode button in TouchView with open modal window

ash/wm/overview/window_selector_controller.h

 // Copyright 2013 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_WM_OVERVIEW_WINDOW_SELECTOR_CONTROLLER_H_
 #define ASH_WM_OVERVIEW_WINDOW_SELECTOR_CONTROLLER_H_
 
 #include <list>
 #include <vector>
 
@@ skipping 14 matching lines @@
 class WindowSelectorTest;
 
 // Manages a window selector which displays an overview of all windows and
 // allows selecting a window to activate it.
 class ASH_EXPORT WindowSelectorController
     : public WindowSelectorDelegate {
  public:
   WindowSelectorController();
   ~WindowSelectorController() override;
 
-  // Returns true if selecting windows in an overview is enabled. This is false
-  // at certain times, such as when the lock screen is visible.
+  // Returns true if the user is in an active desktop environment, i.e., they
+  // are logged in, the screen is not locked, and they are not running in
+  // kiosk mode.
+  static bool IsUserInActiveDesktopEnvironment();
+
+  // Returns true if the user is permitted to engage overview mode (the user
+  // must be in an active desktop environment and must not have any modal
+  // windows open).
   static bool CanSelect();
 
   // Enters overview mode. This is essentially the window cycling mode however
   // not released on releasing the alt key and allows selecting with the mouse
   // or touch rather than keypresses.
   void ToggleOverview();
 
   // Returns true if window selection mode is active.
   bool IsSelecting();
 
@@ skipping 12 matching lines @@
 
   scoped_ptr<WindowSelector> window_selector_;
   base::Time last_selection_time_;
 
   DISALLOW_COPY_AND_ASSIGN(WindowSelectorController);
 };
 
 }  // namespace ash
 
 #endif  // ASH_WM_OVERVIEW_WINDOW_SELECTOR_CONTROLLER_H_