Avoid trying to layout the desktop when its size is set to 0x0 when minimized on Windows.

ui/aura/desktop.h

 // 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.
 
 #ifndef UI_AURA_DESKTOP_H_
 #define UI_AURA_DESKTOP_H_
 #pragma once
 
 #include "base/basictypes.h"
 #include "base/memory/ref_counted.h"
@@ skipping 78 matching lines @@
   // Handles a key event. Returns true if handled.
   bool DispatchKeyEvent(KeyEvent* event);
 
   // Handles a touch event. Returns true if handled.
   bool DispatchTouchEvent(TouchEvent* event);
 
   // Called when the host changes size.
   void OnHostResized(const gfx::Size& size);
 
   // Sets the active window to |window| and the focused window to |to_focus|.
-  // If |to_focus| is NULL, |window| is focused.
-  // |window| can be NULL.
+  // If |to_focus| is NULL, |window| is focused. Does nothing if |window| is
+  // NULL.
   void SetActiveWindow(Window* window, Window* to_focus);
 
   // Activates the topmost window. Does nothing if the topmost window is already
   // active.
   void ActivateTopmostWindow();
 
   // Deactivates |window| and activates the topmost window. Does nothing if
   // |window| is not a topmost window, or there are no other suitable windows to
   // activate.
   void Deactivate(Window* window);
@@ skipping 106 matching lines @@
   Window* mouse_moved_handler_;
   Window* focused_window_;
   Window* touch_event_handler_;
 
   DISALLOW_COPY_AND_ASSIGN(Desktop);
 };
 
 }  // namespace aura
 
 #endif  // UI_AURA_DESKTOP_H_