Ok... I take back the last comment. Taking this out still breaks everything. The key thing this switch does is set where to find manifest.json. By default, manifest.json is searched for next to runtime.js EXCEPT for when the script path starts with "./". When the script path starts with "./", it looks for the manifest.json file in the current directory instead.

It feels like this should be engineered to be more explicit... but does that really need to be done inside this PR?