Replace Helpers.CompletedTask and Helpers.CanceledTask (#446)

src/Microsoft.AspNetCore.Server.HttpSys/Helpers.cs

@@ -14,18 +14,6 @@ namespace Microsoft.AspNetCore.Server.HttpSys
         internal static readonly byte[] ChunkTerminator = new byte[] { (byte)'0', (byte)'\r', (byte)'\n', (byte)'\r', (byte)'\n' };
         internal static readonly byte[] CRLF = new byte[] { (byte)'\r', (byte)'\n' };
 
-        internal static Task CompletedTask()
-        {
-            return Task.FromResult<object>(null);
-        }
-
-        internal static Task<T> CanceledTask<T>()
-        {
-            TaskCompletionSource<T> tcs = new TaskCompletionSource<T>();
-            tcs.TrySetCanceled();
-            return tcs.Task;
-        }
-
         internal static ConfiguredTaskAwaitable SupressContext(this Task task)
         {
             return task.ConfigureAwait(continueOnCapturedContext: false);

src/Microsoft.AspNetCore.Server.HttpSys/RequestProcessing/RequestStream.cs

@@ -306,7 +306,7 @@ namespace Microsoft.AspNetCore.Server.HttpSys
 
             if (cancellationToken.IsCancellationRequested)
             {
-                return Helpers.CanceledTask<int>();
+                return Task.FromCanceled<int>(cancellationToken);
             }
             // TODO: Verbose log parameters
 

src/Microsoft.AspNetCore.Server.HttpSys/RequestProcessing/ResponseBody.cs

@@ -264,7 +264,7 @@ namespace Microsoft.AspNetCore.Server.HttpSys
         {
             if (_disposed)
             {
-                return Helpers.CompletedTask();
+                return Task.CompletedTask;
             }
             return FlushInternalAsync(new ArraySegment<byte>(), cancellationToken);
         }
@@ -274,20 +274,20 @@ namespace Microsoft.AspNetCore.Server.HttpSys
         {
             if (_skipWrites)
             {
-                return Helpers.CompletedTask();
+                return Task.CompletedTask;
             }
 
             var started = _requestContext.Response.HasStarted;
             if (data.Count == 0 && started)
             {
                 // No data to send and we've already sent the headers
-                return Helpers.CompletedTask();
+                return Task.CompletedTask;
             }
 
             if (cancellationToken.IsCancellationRequested)
             {
                 Abort(ThrowWriteExceptions);
-                return Helpers.CanceledTask<int>();
+                return Task.FromCanceled<int>(cancellationToken);
             }
 
             // Make sure all validation is performed before this computes the headers
@@ -535,20 +535,20 @@ namespace Microsoft.AspNetCore.Server.HttpSys
         {
             if (_skipWrites)
             {
-                return Helpers.CompletedTask();
+                return Task.CompletedTask;
             }
 
             var started = _requestContext.Response.HasStarted;
             if (count == 0 && started)
             {
                 // No data to send and we've already sent the headers
-                return Helpers.CompletedTask();
+                return Task.CompletedTask;
             }
 
             if (cancellationToken.IsCancellationRequested)
             {
                 Abort(ThrowWriteExceptions);
-                return Helpers.CanceledTask<int>();
+                return Task.FromCanceled<int>(cancellationToken);
             }
 
             // We are setting buffer size to 1 to prevent FileStream from allocating it's internal buffer