If customization includes default wallpaper, download and apply it.

ash/shell_delegate.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_SHELL_DELEGATE_H_
 #define ASH_SHELL_DELEGATE_H_
 
 #include <string>
 
 #include "ash/ash_export.h"
@@ skipping 115 matching lines @@
 
   // Creates a root window host factory. Shell takes ownership of the returned
   // value.
   virtual WindowTreeHostFactory* CreateWindowTreeHostFactory() = 0;
 
   // Creates a GPU support object. Shell takes ownership of the object.
   virtual GPUSupport* CreateGPUSupport() = 0;
 
   // Get the product name.
   virtual base::string16 GetProductName() const = 0;
+
+  // If device should use customized default wallpaper.
+  virtual bool ShouldUseCustomizedDefaultWallpaper() const = 0;
+
+  // Returns small scale customized wallpaper file name.
+  virtual base::FilePath GetCustomizedWallpaperDefaultRescaledSmallFileName()
+      const = 0;
+
+  // Returns large scale customized wallpaper file name.
+  virtual base::FilePath GetCustomizedWallpaperDefaultRescaledLargeFileName()
+      const = 0;
 };
 
 }  // namespace ash
 
 #endif  // ASH_SHELL_DELEGATE_H_