Update WGSL in tests with renamed builtins

These builtins have been renamed:
* frag_coord -> position
* sample_mask_in -> sample_mask
* sample_mask_out -> sample_mask

Change-Id: Ic40dc9f4e509587b7ac82e43abbf9eec68225d9f
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/48300
Auto-Submit: James Price <jrprice@google.com>
Commit-Queue: Corentin Wallez <cwallez@chromium.org>
Reviewed-by: Corentin Wallez <cwallez@chromium.org>
diff --git a/src/tests/white_box/D3D12DescriptorHeapTests.cpp b/src/tests/white_box/D3D12DescriptorHeapTests.cpp
index 5393e22..7310941 100644
--- a/src/tests/white_box/D3D12DescriptorHeapTests.cpp
+++ b/src/tests/white_box/D3D12DescriptorHeapTests.cpp
@@ -804,7 +804,7 @@
             [[group(0), binding(3)]] var<uniform> buffer0 : U;
 
             [[stage(fragment)]] fn main(
-                [[builtin(frag_coord)]] FragCoord : vec4<f32>
+                [[builtin(position)]] FragCoord : vec4<f32>
             ) -> [[location(0)]] vec4<f32> {
                 return textureSample(texture0, sampler0, FragCoord.xy) + buffer0.color;
             })");