Imported Upstream version 6.4.0.137

Former-commit-id: 943baa9f16a098c33e129777827f3a9d20da00d6

mcs/class/System.Net.Http/corefx/ReadOnlyMemoryContent.cs

@@ -0,0 +1,13 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace System.Net.Http
+{
+    public sealed partial class ReadOnlyMemoryContent : System.Net.Http.HttpContent
+    {
+        public ReadOnlyMemoryContent(System.ReadOnlyMemory<byte> content) => throw new PlatformNotSupportedException();
+        protected internal override System.Threading.Tasks.Task SerializeToStreamAsync(System.IO.Stream stream, System.Net.TransportContext context) => throw new PlatformNotSupportedException();
+        protected internal override bool TryComputeLength(out long length) => throw new PlatformNotSupportedException();
+    }
+}