src/main/java/io/reactivex/Observable.java
@CheckReturnValue
    @SchedulerSupport(SchedulerSupport.COMPUTATION)
    public final ConnectableObservable<T> replay(int bufferSize, long time, TimeUnit unit) {
        return replay(bufferSize, time, unit, Schedulers.computation());
    }
@CheckReturnValue
    @SchedulerSupport(SchedulerSupport.COMPUTATION)
    public final ConnectableObservable<T> replay(int bufferSize, long time, TimeUnit unit) {
        return replay(bufferSize, time, unit, Schedulers.computation());
    }
Returns a {@link ConnectableObservable} that shares a single subscription to the source ObservableSource and
replays at most {@code bufferSize} items that were emitted during a specified time window. A Connectable
ObservableSource resembles an ordinary ObservableSource, except that it does not begin emitting items when it is
subscribed to, but only when its {@code connect} method is called.
<p>
Note that due to concurrency requirements, {@code replay(bufferSize)} may hold strong references to more than
{@code bufferSize} source emissions.
<p>
<img width="640" height="445" src="https://raw.github.com/wiki/ReactiveX/RxJava/images/rx-operators/replay.o.nt.png" alt="">
<dl>
<dt><b>Scheduler:</b></dt>
<dd>This version of {@code replay} operates by default on the {@code computation} {@link Scheduler}.</dd>
</dl>

@param bufferSize
the buffer size that limits the number of items that can be replayed
@param time
the duration of the window in which the replayed items must have been emitted
@param unit
the time unit of {@code time}
@return a {@link ConnectableObservable} that shares a single subscription to the source ObservableSource and
replays at most {@code bufferSize} items that were emitted during the window defined by
{@code time}
@see <a href="http://reactivex.io/documentation/operators/replay.html">ReactiveX operators documentation: Replay</a>