1476848 - Add the ability to capture profiles of long paints

Status: NEW

(Core :: Gecko Profiler, enhancement, P3)

Description

[Jeff Muizelaar [:jrmuizel]]

It would be nice if I could get the profile to only sample during long paints. The API for this could look like:
 - start_gathering()
 - stop_gathering_and_discard()
 - stop_gathering_and_keep()

I would then conditionally call stop_gathering_and_keep() or stop_gathering_and_discard() depending on how long the paint took.

Comment 1

[Markus Stange [:mstange]]

Jeff added some more details when we talked about this in person:
 - This is intended to be a user-visible feature of the gecko profiler, e.g. exposed through a "Long paints only" feature checkbox.
 - He wants to be able to profile for extended durations, e.g. half an hour, and get out a profile that only contains samples for slow paints within those long periods of time.

This last requirement means that we really need to do the sample discarding in the platform at sampling time, and can't just capture a full profile and then do the filtering afterwards in the UI, because such a full profile would be far too large or cover too short amounts of time.