Compressed texture API cleanup


Change-Id: I020bf6e79b5511adbd89931120feb76f359d83aa
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/264056
Reviewed-by: Greg Daniel <egdaniel@google.com>
Reviewed-by: Brian Salomon <bsalomon@google.com>
Commit-Queue: Robert Phillips <robertphillips@google.com>
15 files changed