How to customise downloading UI for on demand instant modules

Currently when requesting another instant module using url deep linking, like so:

```
val intent = Intent(Intent.ACTION_VIEW, uri)
intent.setPackage(applicationContext.packageName)
intent.addCategory(Intent.CATEGORY_BROWSABLE)
startActivity(intent)
```

a progress bar is shown at the top of the screen in a separate activity before the target activity is opened

screenshot:-

Is there a way to customise the downloading UI, to add a downloading text, or branding image, etc.?

Start by reviewing the on-demand instant module flow triggered by the ACTION_VIEW deep link and the separate activity that displays the progress bar. Determine whether that downloading UI supports custom text or branding, and document the supported customization path or the limitation clearly.

Written by the indexing model from the issue text.