Lighthouse: New budget.json API

[khempenius]

Feature wishlist (not comprehensive):

• Better home for CLS
• Reduce over-reliance on the term “budget”
• Syntax for features like UserTiming or FileSize budget

Discussed here:
https://github.com/GoogleChrome/lighthouse/pull/10579

[WebCloud]

Hello @khempenius! One of the things that me and my team have been trying to get done is to closely monitor our custom metrics through lighthouse reports. One possible great addition to the budget.json would be to be able to set a budget for user-timings for that purpose. That way we can assure those metrics don't degrade without any warning 😄.

[khempenius]

Hi @WebCloud, Thanks for the suggestion - this is a great idea. I created a issue for this (though tbh I've been bad at tracking things in Github rather than my head).

More broadly speaking, I think this is a good example of a usage pattern that the new budget.json API needs to address: the syntax for specifying budgets of things like user timings or file size where both a name (performance mark name, file name) and a metric (user-timing, file-size) needs to be supplied.