src/main/java/io/reactivex/Flowable.java
@CheckReturnValue
    @BackpressureSupport(BackpressureKind.ERROR)
    @SchedulerSupport(SchedulerSupport.CUSTOM)
    public final Flowable<T> throttleLast(long intervalDuration, TimeUnit unit, Scheduler scheduler) {
        return sample(intervalDuration, unit, scheduler);
    }
@CheckReturnValue
    @BackpressureSupport(BackpressureKind.ERROR)
    @SchedulerSupport(SchedulerSupport.CUSTOM)
    public final Flowable<T> throttleLast(long intervalDuration, TimeUnit unit, Scheduler scheduler) {
        return sample(intervalDuration, unit, scheduler);
    }
Returns a Flowable that emits only the last item emitted by the source Publisher during sequential
time windows of a specified duration, where the duration is governed by a specified Scheduler.
<p>
This differs from {@link #throttleFirst} in that this ticks along at a scheduled interval whereas
{@link #throttleFirst} does not tick, it just tracks the passage of time.
<p>
<img width="640" height="305" src="https://raw.github.com/wiki/ReactiveX/RxJava/images/rx-operators/throttleLast.s.png" alt="">
<dl>
<dt><b>Backpressure:</b></dt>
<dd>This operator does not support backpressure as it uses time to control data flow.</dd>
<dt><b>Scheduler:</b></dt>
<dd>You specify which {@link Scheduler} this operator will use.</dd>
</dl>

@param intervalDuration
duration of windows within which the last item emitted by the source Publisher will be
emitted
@param unit
the unit of time of {@code intervalDuration}
@param scheduler
the {@link Scheduler} to use internally to manage the timers that handle timeout for each
event
@return a Flowable that performs the throttle operation
@see <a href="http://reactivex.io/documentation/operators/sample.html">ReactiveX operators documentation: Sample</a>
@see <a href="https://github.com/ReactiveX/RxJava/wiki/Backpressure">RxJava wiki: Backpressure</a>
@see #sample(long, TimeUnit, Scheduler)