[Mono.Android] Do not dispose request content stream in AndroidMessageHandler (#8764)

Fixes: #2901
Fixes:  #4476
Fixes: #7086

Neither the `SocketsHttpHandler` nor the `iOS/macOS` `NSUrlSessionHandler` dispose the content stream,
let's follow suit.

Author: simonrozsival

src/Mono.Android/Xamarin.Android.Net/AndroidMessageHandler.cs

@@ -536,30 +536,29 @@ protected virtual async Task WriteRequestContentToOutput (HttpRequestMessage req
 			if (request.Content is null)
 				return;
 
-			using (var stream = await request.Content.ReadAsStreamAsync ().ConfigureAwait (false)) {
-				await stream.CopyToAsync(httpConnection.OutputStream!, 4096, cancellationToken).ConfigureAwait(false);
-
-				//
-				// Rewind the stream to beginning in case the HttpContent implementation
-				// will be accessed again (e.g. after redirect) and it keeps its stream
-				// open behind the scenes instead of recreating it on the next call to
-				// ReadAsStreamAsync. If we don't rewind it, the ReadAsStreamAsync
-				// call above will throw an exception as we'd be attempting to read an
-				// already "closed" stream (that is one whose Position is set to its
-				// end).
-				//
-				// This is not a perfect solution since the HttpContent may do weird
-				// things in its implementation, but it's better than copying the
-				// content into a buffer since we have no way of knowing how the data is
-				// read or generated and also we don't want to keep potentially large
-				// amounts of data in memory (which would happen if we read the content
-				// into a byte[] buffer and kept it cached for re-use on redirect).
-				//
-				// See https://bugzilla.xamarin.com/show_bug.cgi?id=55477
-				//
-				if (stream.CanSeek)
-					stream.Seek (0, SeekOrigin.Begin);
-			}
+			var stream = await request.Content.ReadAsStreamAsync ().ConfigureAwait (false);
+			await stream.CopyToAsync(httpConnection.OutputStream!, 4096, cancellationToken).ConfigureAwait(false);
+
+			//
+			// Rewind the stream to beginning in case the HttpContent implementation
+			// will be accessed again (e.g. after redirect) and it keeps its stream
+			// open behind the scenes instead of recreating it on the next call to
+			// ReadAsStreamAsync. If we don't rewind it, the ReadAsStreamAsync
+			// call above will throw an exception as we'd be attempting to read an
+			// already "closed" stream (that is one whose Position is set to its
+			// end).
+			//
+			// This is not a perfect solution since the HttpContent may do weird
+			// things in its implementation, but it's better than copying the
+			// content into a buffer since we have no way of knowing how the data is
+			// read or generated and also we don't want to keep potentially large
+			// amounts of data in memory (which would happen if we read the content
+			// into a byte[] buffer and kept it cached for re-use on redirect).
+			//
+			// See https://bugzilla.xamarin.com/show_bug.cgi?id=55477
+			//
+			if (stream.CanSeek)
+				stream.Seek (0, SeekOrigin.Begin);
 		}
 
 		internal Task WriteRequestContentToOutputInternal (HttpRequestMessage request, HttpURLConnection httpConnection, CancellationToken cancellationToken)

tests/Mono.Android-Tests/Xamarin.Android.Net/AndroidMessageHandlerTests.cs

@@ -98,6 +98,31 @@ async Task<bool> DoDecompression (string urlPath, string encoding, string jsonFi
 			return true;
 		}
 
+		[Test]
+		public async Task DoesNotDisposeContentStream()
+		{
+			using var listener = new HttpListener ();
+			listener.Prefixes.Add ("http://+:47663/");
+			listener.Start ();
+			listener.BeginGetContext (ar => {
+				var ctx = listener.EndGetContext (ar);
+				ctx.Response.StatusCode = 204;
+				ctx.Response.ContentLength64 = 0;
+				ctx.Response.Close ();
+			}, null);
+
+			var jsonContent = new StringContent ("hello");
+			var request = new HttpRequestMessage (HttpMethod.Post, "http://localhost:47663/") { Content = jsonContent };
+
+			var response = await new HttpClient (new AndroidMessageHandler ()).SendAsync (request);
+			Assert.True (response.IsSuccessStatusCode);
+
+			var contentValue = await jsonContent.ReadAsStringAsync ();
+			Assert.AreEqual ("hello", contentValue);
+
+			listener.Close ();
+		}
+
 		[Test]
 		public async Task ServerCertificateCustomValidationCallback_ApproveRequest ()
 		{