compute top-level property
Spawn an isolate, run
callback on that isolate, passing it
(eventually) return the value returned by
This is useful for operations that take longer than a few milliseconds, and
which would therefore risk skipping frames. For tasks that will only take a
few milliseconds, consider
Q is the type of the message that kicks off the computation.
R is the type of the value returned.
callback argument must be a top-level function, not a closure or an
instance or static method of a class.
There are limitations on the values that can be sent and received to and
from isolates. These limitations constrain the values of
are possible. See the discussion at SendPort.send.
debugLabel argument can be specified to provide a name to add to the
Timeline. This is useful when profiling an application.
final _ComputeImpl compute = _isolates.compute