The USD page is created when the first process (wineboot.exe) completes
its creation, using its provided user_shared_data for initialization.

The server maps the page write-only and the clients map it read-only,
then the server updates the timestamps every 16 ms.

Wine-Bug: https://bugs.winehq.org/show_bug.cgi?id=29168Signed-off-by: Rémi Bernon <rbernon@codeweavers.com>
Signed-off-by: Alexandre Julliard <julliard@winehq.org>