When a Flutter web engine promise is rejected for whatever reason, it is rendered to the JS Console as a Warning, which makes it harder to see around other browser notifications, for example:

The whole explanation for "Uncaught (in promise)" is right above it, but hard to spot because it looks like every other browser warning in the console.

We do this here:

• https://github.com/flutter/engine/blob/d4850c1ae648e1265ea7a9dd679918ec40324188/lib/web_ui/lib/src/engine/js_interop/js_promise.dart#L33

printWarning is defined here:

• https://github.com/flutter/engine/blob/d4850c1ae648e1265ea7a9dd679918ec40324188/lib/web_ui/lib/src/engine/util.dart#L524-L528

I think we should console.error the error messages of those promises, so they show up closer to what they look like in JS: