Brandon Jones 145f865fb1 Add texture_external parsing and intrinsic overloads
Adds texture_external to ParserImpl. Adds texture_external overloads to
TextureSample, TextureLoad, and TextureDimensions to the intrisic table.
Adds corresponding tests.

Bug: dawn:728
Change-Id: I5e5557a10327f8c3d3044319decd748f812ecf3e
Reviewed-on: https://dawn-review.googlesource.com/c/tint/+/48722
Reviewed-by: Ben Clayton <bclayton@google.com>
Kokoro: Kokoro <noreply+kokoro@google.com>
Commit-Queue: Ben Clayton <bclayton@google.com>
2021-04-22 22:47:03 +00:00
..
2021-03-17 18:49:03 +00:00