1991109 - Capture Startup Timeline Event START on Android, report as telemetry for cold applinks

Status: NEW

(Core :: Audio/Video, enhancement, P3)

Description

[Andrew Creskey [:acreskey]]

We have started collect android cold process applink telemetry (bug 1990344, bug 1966167).

In looking into this, gecko already maintains a startup timeline of events.
These would would be useful on Android for applink startup:

  mozilla_StartupTimeline_Event(START, "start")
  mozilla_StartupTimeline_Event(MAIN, "main")

https://searchfox.org/firefox-main/rev/fd531836ca5e48e18a5afc171418bcbcb9d268e2/toolkit/components/startup/StartupTimeline.h#8-9

MAIN is already being recorded for desktop and android, here:
https://searchfox.org/firefox-main/rev/fd531836ca5e48e18a5afc171418bcbcb9d268e2/toolkit/xre/nsAppRunner.cpp#3988

So we just need to mark the START point, and collect the telemety for cold applink, similar to bug 1990344