If customization includes default wallpaper, download and apply it.

ash/shell/shell_delegate_impl.cc

Index: ash/shell/shell_delegate_impl.cc
diff --git a/ash/shell/shell_delegate_impl.cc b/ash/shell/shell_delegate_impl.cc
index d21f7acb7f3a89552de1365518fa65624173f9f7..a74a74f6ef78cf2d785414dec2a3e7770f30f00e 100644
--- a/ash/shell/shell_delegate_impl.cc
+++ b/ash/shell/shell_delegate_impl.cc
@@ -170,5 +170,19 @@ base::string16 ShellDelegateImpl::GetProductName() const {
   return base::string16();
 }
 
+bool ShellDelegateImpl::ShouldUseCustomizedDefaultWallpaper() const {
+  return false;
+}
+
+base::FilePath
+ShellDelegateImpl::GetCustomizedWallpaperDefaultRescaledSmallFileName() const {
+  return base::FilePath();
+}
+
+base::FilePath
+ShellDelegateImpl::GetCustomizedWallpaperDefaultRescaledLargeFileName() const {
+  return base::FilePath();
+}
+
 }  // namespace shell
 }  // namespace ash