[FR]: Performance: Allow adding custom attributes to built-in traces

[mikeger]

Description

Firebase performance is tracking the number of built-in events, such as

• App lifecycle (_app_start,_app_in_background, _app_in_foreground)
• Network requests
• Time spent on a screen

Currently, it is not possible to assign custom attributes to those traces. It would be great to allow this. Luckily, it is a mere question of making an API public.

API Proposal

Performance class has private compliance to PerformanceAttributable (FRPerformanceAttributable). If this compliance would be public, it would be possible to set the attributes on the Performance singleton, which are in turn propagated as default attributes for all traces.

Firebase Product(s)

Performance

[google-oss-bot]

I couldn't figure out how to label this issue, so I've labeled it for a human to triage. Hang tight.

[bidrohi]

This is already available to use in the Android SDK, so would be great to have it in the iOS one too.