BackgroundTaskRunner - more fixes

src/Umbraco.Web/Scheduling/ThreadingTaskImmutable.cs

@@ -0,0 +1,44 @@
+using System;
+using System.Runtime.CompilerServices;
+using System.Threading.Tasks;
+
+namespace Umbraco.Web.Scheduling
+{
+    /// <summary>
+    /// Wraps a Task within an object that gives access to its GetAwaiter method and Status
+    /// property while ensuring that it cannot be modified in any way.
+    /// </summary>
+    internal class ThreadingTaskImmutable
+    {
+        private readonly Task _task;
+
+        /// <summary>
+        /// Initializes a new instance of the <see cref="ThreadingTaskImmutable"/> class with a Task.
+        /// </summary>
+        /// <param name="task">The task.</param>
+        public ThreadingTaskImmutable(Task task)
+        {
+            if (task == null)
+                throw new ArgumentNullException("task");
+            _task = task;
+        }
+
+        /// <summary>
+        /// Gets an awaiter used to await the task.
+        /// </summary>
+        /// <returns>An awaiter instance.</returns>
+        public TaskAwaiter GetAwaiter()
+        {
+            return _task.GetAwaiter();
+        }
+
+        /// <summary>
+        /// Gets the TaskStatus of the task.
+        /// </summary>
+        /// <returns>The current TaskStatus of the task.</returns>
+        public TaskStatus Status
+        {
+            get { return _task.Status; }
+        }
+    }
+}