src/main/java/io/reactivex/Observable.java
@CheckReturnValue
    @SchedulerSupport(SchedulerSupport.NONE)
    public final Observable<List<T>> buffer(int count, int skip) {
        return buffer(count, skip, ArrayListSupplier.<T>asCallable());
    }
@CheckReturnValue
    @SchedulerSupport(SchedulerSupport.NONE)
    public final Observable<List<T>> buffer(int count, int skip) {
        return buffer(count, skip, ArrayListSupplier.<T>asCallable());
    }
Returns an Observable that emits buffers of items it collects from the source ObservableSource. The resulting
ObservableSource emits buffers every {@code skip} items, each containing {@code count} items. When the source
ObservableSource completes, the resulting ObservableSource emits the current buffer and propagates the notification
from the source ObservableSource. Note that if the source ObservableSource issues an onError notification
the event is passed on immediately without first emitting the buffer it is in the process of assembling.
<p>
<img width="640" height="320" src="https://raw.github.com/wiki/ReactiveX/RxJava/images/rx-operators/buffer4.png" alt="">
<dl>
<dt><b>Scheduler:</b></dt>
<dd>This version of {@code buffer} does not operate by default on a particular {@link Scheduler}.</dd>
</dl>

@param count
the maximum size of each buffer before it should be emitted
@param skip
how many items emitted by the source ObservableSource should be skipped before starting a new
buffer. Note that when {@code skip} and {@code count} are equal, this is the same operation as
{@link #buffer(int)}.
@return an Observable that emits buffers for every {@code skip} item from the source ObservableSource and
containing at most {@code count} items
@see <a href="http://reactivex.io/documentation/operators/buffer.html">ReactiveX operators documentation: Buffer</a>