src/main/java/io/reactivex/Observable.java
@CheckReturnValue
    @SchedulerSupport(SchedulerSupport.CUSTOM)
    public final Observable<T> skipLast(long time, TimeUnit unit, Scheduler scheduler) {
        return skipLast(time, unit, scheduler, false, bufferSize());
    }
@CheckReturnValue
    @SchedulerSupport(SchedulerSupport.CUSTOM)
    public final Observable<T> skipLast(long time, TimeUnit unit, Scheduler scheduler) {
        return skipLast(time, unit, scheduler, false, bufferSize());
    }
Returns an Observable that drops items emitted by the source ObservableSource during a specified time window
(defined on a specified scheduler) before the source completes.
<p>
<img width="640" height="340" src="https://raw.github.com/wiki/ReactiveX/RxJava/images/rx-operators/skipLast.ts.png" alt="">
<p>
Note: this action will cache the latest items arriving in the specified time window.
<dl>
<dt><b>Scheduler:</b></dt>
<dd>You specify which {@link Scheduler} this operator will use for tracking the current time</dd>
</dl>

@param time
the length of the time window
@param unit
the time unit of {@code time}
@param scheduler
the scheduler used as the time source
@return an Observable that drops those items emitted by the source ObservableSource in a time window before the
source completes defined by {@code time} and {@code scheduler}
@see <a href="http://reactivex.io/documentation/operators/skiplast.html">ReactiveX operators documentation: SkipLast</a>