Replace D24_UNORM with a packed version. Adding an explicit X8 channel packs the format into 32 bits. This gives the correct 4-byte alignment instead of a mysterious 3-byte version. Bug: angleproject:2729 Change-Id: Id38f74db4ba61c500baeb6526a9d14e1d31d4363 Reviewed-on: https://chromium-review.googlesource.com/1140739 Reviewed-by: Geoff Lang <geofflang@chromium.org> Commit-Queue: Jamie Madill <jmadill@chromium.org>