Use TextureFormat::None for RenderBundleEncoder and AttachmentState

Bug: dawn:214
Change-Id: Ia9432582b0a5627c00d46ebcfa63ebf1ba246651
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/10520
Commit-Queue: Kai Ninomiya <kainino@chromium.org>
Reviewed-by: Corentin Wallez <cwallez@chromium.org>
diff --git a/dawn.json b/dawn.json
index 7e03a5f..8d4851f 100644
--- a/dawn.json
+++ b/dawn.json
@@ -857,7 +857,7 @@
         "members": [
             {"name": "color formats count", "type": "uint32_t"},
             {"name": "color formats", "type": "texture format", "annotation": "const*", "length": "color formats count"},
-            {"name": "depth stencil format", "type": "texture format", "annotation": "const*", "optional": true},
+            {"name": "depth stencil format", "type": "texture format", "default": "none"},
             {"name": "sample count", "type": "uint32_t", "default": "1"}
         ]
     },