Initial IAsyncScheduler interface.

AsyncRx.NET/System.Reactive.Async/System/Reactive/Concurrency/IAsyncScheduler.cs

@@ -2,9 +2,15 @@
 // The .NET Foundation licenses this file to you under the Apache 2.0 License.
 // See the LICENSE file in the project root for more information. 
 
+using System.Threading;
+using System.Threading.Tasks;
+
 namespace System.Reactive.Concurrency
 {
     public interface IAsyncScheduler : IClock
     {
+        Task<IAsyncDisposable> ScheduleAsync(Func<CancellationToken, Task> action);
+        Task<IAsyncDisposable> ScheduleAsync(Func<CancellationToken, Task> action, TimeSpan dueTime);
+        Task<IAsyncDisposable> ScheduleAsync(Func<CancellationToken, Task> action, DateTimeOffset dueTime);
     }
 }