add test and fix #3254 (#3255)

* add test and fix #3254

* remove continueWithExtra

* add timeout attribute

* don't delegate the cancellationtoken to the operationcancelledexception.

* Revert "add timeout attribute"

This reverts commit aeeaa50.

* Update control.fs

Author: matthid

src/fsharp/FSharp.Core.Unittests/FSharp.Core/Microsoft.FSharp.Control/AsyncType.fs

@@ -162,7 +162,22 @@ type AsyncType() =
         this.WaitASec t
         Assert.IsTrue (t.IsCompleted)
         Assert.AreEqual(s, t.Result)    
-      
+
+    [<Test>]
+    member this.RunSynchronouslyCancellationWithDelayedResult () =
+        let cts = new CancellationTokenSource()
+        let tcs = TaskCompletionSource<int>()
+        let _ = cts.Token.Register(fun () -> tcs.SetResult 42)
+        let a = async {
+            cts.CancelAfter (100)
+            let! result = tcs.Task |> Async.AwaitTask
+            return result }
+
+        try
+            Async.RunSynchronously(a, cancellationToken = cts.Token)
+                |> ignore
+        with :? OperationCanceledException as o -> ()
+
     [<Test>]
     member this.ExceptionPropagatesToTask () =
         let a = async { 

src/fsharp/FSharp.Core/control.fs

@@ -1536,14 +1536,6 @@ namespace Microsoft.FSharp.Control
     // Contains helpers that will attach continuation to the given task.
     // Should be invoked as a part of protectedPrimitive(withResync) call
     module TaskHelpers = 
-        let private continueWithExtra token =
-#if FSCORE_PORTABLE_OLD || FSCORE_PORTABLE_NEW
-            token |> ignore
-            TaskContinuationOptions.None
-#else
-            token
-#endif
-
         let continueWith (task : Task<'T>, args, useCcontForTaskCancellation) = 
 
             let continuation (completedTask : Task<_>) : unit =
@@ -1557,7 +1549,7 @@ namespace Microsoft.FSharp.Control
                     else
                         args.cont completedTask.Result)) |> unfake
 
-            task.ContinueWith(Action<Task<'T>>(continuation), continueWithExtra args.aux.token) |> ignore |> fake
+            task.ContinueWith(Action<Task<'T>>(continuation)) |> ignore |> fake
 
         let continueWithUnit (task : Task, args, useCcontForTaskCancellation) = 
 
@@ -1572,7 +1564,7 @@ namespace Microsoft.FSharp.Control
                     else
                         args.cont ())) |> unfake
 
-            task.ContinueWith(Action<Task>(continuation), continueWithExtra args.aux.token) |> ignore |> fake
+            task.ContinueWith(Action<Task>(continuation)) |> ignore |> fake
 #endif
 
 #if FX_NO_REGISTERED_WAIT_HANDLES