If a resource is marked MayNeedInit, then we don't serialize it but
mark the data as not initialized.

Bug: angleproject:6041
Change-Id: If3d3431a58848f7835692fe10b30fab68c901d8a
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2976657Reviewed-by: Cody Northrop <cnorthrop@google.com>
Reviewed-by: Jamie Madill <jmadill@chromium.org>
Commit-Queue: Gert Wollny <gert.wollny@collabora.com>