When the two channels don't receive for a while, call DoWork forcibly to avoid
freeze.
In theory, this timeout should not be necessary. However, it looks like this
'select' statement sometimes blocks forever on some Android devices like
Pixel 4(a). Apparently workAvailable sometimes not receives even though there
are queued OpenGL functions. Call DoWork for such case as a symptomatic
treatment.
Calling DoWork without waiting for workAvailable is safe. If there are no tasks,
DoWork should return immediately.
Updates #1322Fixes#1332
20ccafce4b