Imported Upstream version 3.6.0

Former-commit-id: da6be194a6b1221998fc28233f2503bd61dd9d14

external/rx/Ix/NET/System.Interactive/IAwaitable.cs

@@ -0,0 +1,23 @@
+// Copyright (c) Microsoft Open Technologies, Inc. All rights reserved. See License.txt in the project root for license information.
+#if HAS_AWAIT
+using System;
+using System.Collections.Generic;
+using System.Diagnostics;
+using System.Runtime.CompilerServices;
+using System.Threading;
+using System.Threading.Tasks;
+
+namespace System.Linq
+{
+    public interface IAwaitable
+    {
+        IAwaiter GetAwaiter();
+    }
+
+    public interface IAwaiter : ICriticalNotifyCompletion
+    {
+        bool IsCompleted { get; }
+        void GetResult();
+    }
+}
+#endif