Fixes in ReadPixels2 and yuv_texture gm to fix Vulkan validation issues.

Bug: skia:
Change-Id: Idfccdec9106bdc79a690da0e173a232a0cbe51a9
Reviewed-on: https://skia-review.googlesource.com/122955
Reviewed-by: Brian Salomon <bsalomon@google.com>
Commit-Queue: Greg Daniel <egdaniel@google.com>
2 files changed