aura/ash cleanup: Use a single window-key for constrained windows.

ash/ash_constants.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_ASH_CONSTANTS_H_
 #define ASH_ASH_CONSTANTS_H_
 
 #include "ash/ash_export.h"
 #include "ui/aura/window.h"
 #include "ui/base/ui_base_types.h"
 
 typedef unsigned int SkColor;
 
 namespace ash {
 
-// The window is a constrained window and lives therefore entirely within
-// another aura window.
-ASH_EXPORT extern const aura::WindowProperty<bool>* const
-    kConstrainedWindowKey;
-
 // In the window corners, the resize areas don't actually expand bigger, but the
 // 16 px at the end of each edge triggers diagonal resizing.
 ASH_EXPORT extern const int kResizeAreaCornerSize;
 
 // Ash windows do not have a traditional visible window frame. Window content
 // extends to the edge of the window. We consider a small region outside the
 // window bounds and an even smaller region overlapping the window to be the
 // "non-client" area and use it for resizing.
 ASH_EXPORT extern const int kResizeOutsideBoundsSize;
 ASH_EXPORT extern const int kResizeOutsideBoundsScaleForTouch;
 ASH_EXPORT extern const int kResizeInsideBoundsSize;
 
 #if defined(OS_CHROMEOS)
 // Background color used for the Chrome OS boot splash screen.
 extern const SkColor kChromeOsBootColor;
 #endif
 
 // The border color of keyboard focus for launcher items and system tray.
 extern const SkColor kFocusBorderColor;
 
 } // namespace ash
 
 #endif  // ASH_ASH_CONSTANTS_H_