Introduces the majority of the logic associated with enabling
multiplanar external textures. Removes most backend logic associated
with external textures in favor of expanding them into their components
in the frontend. Includes a basic e2e test demonstrating multiplanar
YUV-to-RGB conversion.
Bug: dawn:1082
Change-Id: Ib5c042e5639b1a8efe2954680abc346c8c6c76d7
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/78248
Reviewed-by: Austin Eng <enga@chromium.org>
Reviewed-by: Corentin Wallez <cwallez@chromium.org>
Commit-Queue: Brandon1 Jones <brandon1.jones@intel.com>
