Add WebGPU CTS dep and build files

These build files are not yet used, but intended to be included by a
build file in Chromium. The test expectations file will move here too,
allowing Dawn/Tint changes to adjust test expectations in the same CL.

Bug: chromium:1306640
Change-Id: Id0be5c155ec7c79252e724cd64e54d1ea9f3dbda
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/83761
Reviewed-by: Austin Eng <enga@chromium.org>
Commit-Queue: Kai Ninomiya <kainino@chromium.org>
diff --git a/DEPS b/DEPS
index ffd20b2..27ac111 100644
--- a/DEPS
+++ b/DEPS
@@ -152,6 +152,12 @@
     'condition': 'dawn_standalone',
   },
 
+  # WebGPU CTS - not used directly by Dawn, only transitively by Chromium.
+  'third_party/webgpu-cts': {
+    'url': '{chromium_git}/external/github.com/gpuweb/cts@90654f28f4092a4993e91726cb18f697aefb201f',
+    'condition': 'build_with_chromium',
+  },
+
   # Dependencies required to build Dawn NodeJS bindings
   'third_party/node-api-headers': {
     'url': '{github_git}/nodejs/node-api-headers.git@d68505e4055ecb630e14c26c32e5c2c65e179bba',