Fix leak of textures in wacky_yuv_* GMs

Change-Id: Ie3e303348c25ac387a6d461b8b8d15ea63210627
Reviewed-on: https://skia-review.googlesource.com/c/187926
Reviewed-by: Greg Daniel <egdaniel@google.com>
Reviewed-by: Robert Phillips <robertphillips@google.com>
Commit-Queue: Brian Salomon <bsalomon@google.com>
1 file changed