To determine Time to Consistently Interactive [1], we need to keep tracing until we reach network and main thread quiescence, which is currently defined as 5 seconds of no more than 2 network requests and no main thread task longer than 50ms. This is hard to do today because not all devtools network request and main thread task signals are sent as they happen, and even if they were, determining this quiescence requires complex calculations. 

Since TTCI will be implemented as an UMA and therefore need to detect this quiescence in the browser anyway, we should plumb this quiescence signal all the way to devtools so that devtools and lighthouse can use it as a useful criterion to stop tracing. 


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[1] https://docs.google.com/document/d/1GGiI9-7KeY3TPqS3YT271upUVimo-XiL5mwWorDUD4c/edit?usp=sharing