Minimize black screen during the boot with multi displays

ash/desktop_background/desktop_background_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_DESKTOP_BACKGROUND_DESKTOP_BACKGROUND_CONTROLLER_H_
 #define ASH_DESKTOP_BACKGROUND_DESKTOP_BACKGROUND_CONTROLLER_H_
 
 #include "ash/ash_export.h"
 #include "base/basictypes.h"
 #include "base/memory/scoped_ptr.h"
@@ skipping 46 matching lines @@
 ASH_EXPORT extern const int kLargeWallpaperMaxWidth;
 ASH_EXPORT extern const int kLargeWallpaperMaxHeight;
 
 class DesktopBackgroundControllerObserver;
 
 // Loads selected desktop wallpaper from file system asynchronously and updates
 // background layer if loaded successfully.
 class ASH_EXPORT DesktopBackgroundController : public aura::WindowObserver {
  public:
   enum BackgroundMode {
+    BACKGROUND_NONE,
     BACKGROUND_IMAGE,
     BACKGROUND_SOLID_COLOR
   };
 
   DesktopBackgroundController();
   virtual ~DesktopBackgroundController();
 
   // Gets the desktop background mode.
   BackgroundMode desktop_background_mode() const {
     return desktop_background_mode_;
@@ skipping 108 matching lines @@
   scoped_refptr<WallpaperLoader> wallpaper_loader_;
 
   base::WeakPtrFactory<DesktopBackgroundController> weak_ptr_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(DesktopBackgroundController);
 };
 
 }  // namespace ash
 
 #endif  // ASH_DESKTOP_BACKGROUND_DESKTOP_BACKGROUND_CONTROLLER_H_