Fix gl copyTexSubImage format requirements.

Add checks for compatible channels and format types.

Bug:skia:10863
Change-Id: I44f9310097007c3ed70f94e949b10612a2fe2643
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/329421
Reviewed-by: Brian Salomon <bsalomon@google.com>
Reviewed-by: Alexis Hetu <sugoi@google.com>
Commit-Queue: Greg Daniel <egdaniel@google.com>
2 files changed