Add support for Android creation of protected Vk backend contexts

Change-Id: I59fb63cac98da9f58c2fe058a5999326bf906555
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/735198
Reviewed-by: Greg Daniel <egdaniel@google.com>
Commit-Queue: Robert Phillips <robertphillips@google.com>
2 files changed