skip content-length on DELETE and OPTIONS methods with no body

src/System.Net.Http/src/System/Net/Http/HttpMethod.cs

@@ -174,7 +174,8 @@ internal bool MustHaveRequestBody
                 // Normalize before calling this
                 Debug.Assert(ReferenceEquals(this, Normalize(this)));
 
-                return !ReferenceEquals(this, HttpMethod.Get) && !ReferenceEquals(this, HttpMethod.Head) && !ReferenceEquals(this, HttpMethod.Connect);
+                return !ReferenceEquals(this, HttpMethod.Get) && !ReferenceEquals(this, HttpMethod.Head) && !ReferenceEquals(this, HttpMethod.Connect) &&
+                       !ReferenceEquals(this, HttpMethod.Options) && !ReferenceEquals(this, HttpMethod.Delete);
             }
         }
     }

src/System.Net.Http/tests/FunctionalTests/HttpRequestMessageTest.cs

@@ -3,16 +3,18 @@
 // See the LICENSE file in the project root for more information.
 
 using System;
+using System.Collections.Generic;
 using System.IO;
 using System.Net.Http.Headers;
+using System.Net.Test.Common;
 using System.Threading;
 using System.Threading.Tasks;
 
 using Xunit;
 
 namespace System.Net.Http.Functional.Tests
 {
-    public class HttpRequestMessageTest
+    public class HttpRequestMessageTest : HttpClientTestBase
     {
         Version _expectedRequestMessageVersion = !PlatformDetection.IsFullFramework ? new Version(2,0) : new Version(1, 1);
 
@@ -215,6 +217,43 @@ public void ToString_DefaultAndNonDefaultInstance_DumpAllFields()
                 "}", rm.ToString());
         }
 
+        [Theory]
+        [InlineData("DELETE")]
+        [InlineData("OPTIONS")]
+        [InlineData("HEAD")]
+        public async Task HttpRequest_BodylessMethod_NoContentLength(string method)
+        {
+            if (IsWinHttpHandler || IsNetfxHandler || IsUapHandler)
+            {
+                // Some platform handlers differ but we don't take it as failure.
+                return;
+            }
+
+            using (HttpClient client = new HttpClient())
+            {
+                await LoopbackServer.CreateServerAsync(async (server, uri) =>
+                {
+                    var request = new HttpRequestMessage();
+                    request.RequestUri = uri;
+                    request.Method = new HttpMethod(method);
+
+                    Task<HttpResponseMessage> requestTask = client.SendAsync(request);
+                    await server.AcceptConnectionAsync(async connection =>
+                    {
+                        List<string> headers = await connection.ReadRequestHeaderAsync();
+                        foreach (string line in headers)
+                        {
+                            // There should be no Content-Length header.
+                            Assert.False(line.StartsWith("Content-length:", StringComparison.InvariantCultureIgnoreCase));
+                        }
+
+                        await connection.SendResponseAsync();
+                        await requestTask;
+                    });
+                });
+            }
+        }
+
         #region Helper methods
 
         private class MockContent : HttpContent