Fixes for Emscripten generators

Bug: none
Change-Id: I9b4f7843e2b401776a868d33335a9df027c13511
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/24881
Reviewed-by: Corentin Wallez <cwallez@chromium.org>
Commit-Queue: Corentin Wallez <cwallez@chromium.org>

dawn.json

@@ -430,7 +430,7 @@
     "compare function": {
         "category": "enum",
         "values": [
-            {"value": 0, "name": "undefined"},
+            {"value": 0, "name": "undefined", "jsrepr": "undefined"},
             {"value": 1, "name": "never"},
             {"value": 2, "name": "less"},
             {"value": 3, "name": "less equal"},

generator/templates/webgpu_struct_info.json

@@ -23,14 +23,13 @@
         "defines": [],
         "structs": {
             "WGPUChainedStruct": [
-                "nextInChain",
+                "next",
                 "sType"
             ],
             {% for type in by_category["structure"] if type.javascript %}
                 "{{as_cType(type.name)}}": [
                     {% if type.chained %}
-                        "nextInChain",
-                        "sType"
+                        "chain"
                     {%- elif type.extensible %}
                         "nextInChain"
                     {%- endif %}