If customization includes default wallpaper, download and apply it.

chrome/browser/chromeos/extensions/wallpaper_api.cc

 // 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.
 
 #include "chrome/browser/chromeos/extensions/wallpaper_api.h"
 
 #include "ash/desktop_background/desktop_background_controller.h"
 #include "base/file_util.h"
 #include "base/lazy_instance.h"
 #include "base/path_service.h"
@@ skipping 160 matching lines @@
   chromeos::UserImage wallpaper(*image.get());
   if (!base::PathExists(thumbnail_path.DirName()))
     base::CreateDirectory(thumbnail_path.DirName());
 
   scoped_refptr<base::RefCountedBytes> data;
   chromeos::WallpaperManager::Get()->ResizeWallpaper(
       wallpaper,
       ash::WALLPAPER_LAYOUT_STRETCH,
       ash::kWallpaperThumbnailWidth,
       ash::kWallpaperThumbnailHeight,
-      &data);
+      &data,
+      NULL);
   BrowserThread::PostTask(
       BrowserThread::UI, FROM_HERE,
       base::Bind(
           &WallpaperSetWallpaperFunction::ThumbnailGenerated,
           this, data));
 }
 
 void WallpaperSetWallpaperFunction::ThumbnailGenerated(
     base::RefCountedBytes* data) {
   BinaryValue* result = BinaryValue::CreateWithCopiedBuffer(
       reinterpret_cast<const char*>(data->front()), data->size());
   SetResult(result);
   SendResponse(true);
 }
 
 void WallpaperSetWallpaperFunction::OnWallpaperFetched(
     bool success,
     const std::string& response) {
   if (success) {
     params_->details.wallpaper_data.reset(new std::string(response));
     StartDecode(*params_->details.wallpaper_data);
   } else {
     SetError(response);
     SendResponse(false);
   }
 }