Reflatten YUVA image on each request.

It should now be rare to require a RGBA texture from a YUVA image (e.g.
in image filter)

Removes a thread-safety issue. A step towards allowing clients to pump
new data into the planes and be sure Skia wont draw the old contents.

Bug: skia:11873

Change-Id: I007cf28e477155f85ed9f1c6cc4547f9dbbb73fd
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/397319
Commit-Queue: Brian Salomon <bsalomon@google.com>
Reviewed-by: Robert Phillips <robertphillips@google.com>
4 files changed