This can be useful if we know when an event happened, but our code isn't
running at that time (such as reporting when an image was presented in
the wayland wsi).
We can't really mix these with events that we log at the current time,
because there could be overlap, so also add a function for creating
custom tracks.
Signed-off-by: Derek Foreman <derek.foreman@collabora.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/28634>
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