test: Add some basic vector / matrix access tests

Change-Id: I774d7e4b6fdf9d1507bd9cbf3be00bd4113e8162
Reviewed-on: https://dawn-review.googlesource.com/c/tint/+/51222
Kokoro: Kokoro <noreply+kokoro@google.com>
Reviewed-by: David Neto <dneto@google.com>
Commit-Queue: Ben Clayton <bclayton@google.com>
diff --git a/test/access/var/vector.wgsl.expected.hlsl b/test/access/var/vector.wgsl.expected.hlsl
new file mode 100644
index 0000000..d978bae
--- /dev/null
+++ b/test/access/var/vector.wgsl.expected.hlsl
@@ -0,0 +1,9 @@
+[numthreads(1, 1, 1)]
+void main() {
+  float3 v;
+  const float scalar = v.y;
+  const float2 swizzle2 = v.xz;
+  const float3 swizzle3 = v.xzy;
+  return;
+}
+