During the processing of a continuous drag event, other mouse move
events may be in the queue waiting to be processed.
But when a mouse wrapping happens, these waiting mouse move events
become out of date as they report a mouse position prior to wrapping.
The current code ignores these events by comparing their `timestamp` to
the time recorded in the last mouse wrapping.
The bug happens because the computed value in
`mach_absolute_time() * 1e-9` for some reason is incompatible with the
value of `[event timestamp]`.
Since macOS 10.6, we have a new way to get the amount of time the
system has been awake. `[[NSProcessInfo processInfo] systemUptime]`.
Using this updated method fixed the problem.
Differential Revision: https://developer.blender.org/D12202
215734bc52