ReadonlyappApp process start (epoch ms).
ReadonlyforegroundCurrent foreground-session start (epoch ms); the first request after it reports the elapsed time.
Optional ReadonlynavigationSession navigation state; falls back to its current screen when no surfaceModule is given.
Readonlyrequestclient_recorded_request_time_ms as a number.
Optional ReadonlysurfaceAnalytics module of the surface this request belongs to. The feed surfaces
report the surface they are loading (feed_timeline), which the app records
in its session navigation trail before the client-endpoint screen flips.
Everything the
session_level_signalsblob needs: the request clock and the app/session navigation state.