Replace hardcode content with metadata defined in api.json
BUG=dawn:1201
Change-Id: Ib6d6a9c7afc8fb89d3ff2d0129dbfba04adb542a
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/73160
Reviewed-by: Corentin Wallez <cwallez@chromium.org>
Reviewed-by: Austin Eng <enga@chromium.org>
Commit-Queue: Junwei Fu <junwei.fu@intel.com>