Motivation
Currently when future tasks are scheduled via schedule(Runnable, ...)
methods, the supplied Runnable is wrapped in a newly allocated Callable
adapter prior to being wrapped in a ScheduledFutureTask.
This can be avoided which saves an object allocation per scheduled task.
Modifications
Change the Callable task field of ScheduledFutureTask to be of type
Object so that it can hold/run Runnables directly in addition to
Callables.
An "adapter" is still used in the case a Runnable is scheduled with an
explicit constant non-null completion value, assumed to be rare.
Result
Less garbage
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