Enable transfer from texture to buffer on ANGLE.

This is necessary to support the async readback API on Windows Chrome.

Transfer from buffer to texture is still disabled as the unit test
still fails.

Bug: chromium:1040643

Change-Id: I0e16437c066fadfdd8dbbbcaf376c6901a538063
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/263528
Commit-Queue: Brian Salomon <bsalomon@google.com>
Reviewed-by: Robert Phillips <robertphillips@google.com>
8 files changed