If customization includes default wallpaper, download and apply it.

chrome/browser/chromeos/extensions/wallpaper_private_api.cc

Index: chrome/browser/chromeos/extensions/wallpaper_private_api.cc
diff --git a/chrome/browser/chromeos/extensions/wallpaper_private_api.cc b/chrome/browser/chromeos/extensions/wallpaper_private_api.cc
index fa4c567d0b084d38aa34efcf51a8b9f4a32d8fb6..64c33a08acb25f65dcea81e76d8a2bb8da775e73 100644
--- a/chrome/browser/chromeos/extensions/wallpaper_private_api.cc
+++ b/chrome/browser/chromeos/extensions/wallpaper_private_api.cc
@@ -445,7 +445,8 @@ void WallpaperPrivateSetWallpaperFunction::SaveToFile() {
         file_path,
         ash::WALLPAPER_LAYOUT_CENTER_CROPPED,
         ash::kSmallWallpaperMaxWidth,
-        ash::kSmallWallpaperMaxHeight);
+        ash::kSmallWallpaperMaxHeight,
+        NULL);
   } else {
     std::string error = base::StringPrintf(
         "Failed to create/write wallpaper to %s.", file_name.c_str());
@@ -588,7 +589,8 @@ void WallpaperPrivateSetCustomWallpaperFunction::GenerateThumbnail(
       ash::WALLPAPER_LAYOUT_STRETCH,
       ash::kWallpaperThumbnailWidth,
       ash::kWallpaperThumbnailHeight,
-      &data);
+      &data,
+      NULL);
   BrowserThread::PostTask(
         BrowserThread::UI, FROM_HERE,
         base::Bind(