Support luminance-alpha GL format for YUVA planes

Bug: skia:10632
Change-Id: Ic91510b55644c15ee4eb5f96e7c35193b5ce49df
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/344761
Commit-Queue: Brian Salomon <bsalomon@google.com>
Reviewed-by: Greg Daniel <egdaniel@google.com>
15 files changed