HttpHandlerDiagnosticListener did not send DiagnosticSource Stop event on netfx in W3C mode

src/System.Diagnostics.DiagnosticSource/src/System/Diagnostics/HttpHandlerDiagnosticListener.cs

@@ -658,7 +658,8 @@ private void RaiseResponseEvent(HttpWebRequest request, HttpWebResponse response
             // Response event could be received several times for the same request in case it was redirected
             // IsLastResponse checks if response is the last one (no more redirects will happen)
             // based on response StatusCode and number or redirects done so far
-            if (request.Headers.Get(RequestIdHeaderName) != null && IsLastResponse(request, response.StatusCode))
+            bool wasRequestInstrumented = request.Headers.Get(TraceParentHeaderName) != null || request.Headers.Get(RequestIdHeaderName) != null;
+            if (wasRequestInstrumented && IsLastResponse(request, response.StatusCode))
             {
                 // only send Stop if request was instrumented
                 this.Write(RequestStopName, new { Request = request, Response = response });

src/System.Diagnostics.DiagnosticSource/tests/HttpHandlerDiagnosticListenerTests.cs

@@ -173,6 +173,15 @@ public async Task TestW3CHeaders()
                     Assert.Matches("^[0-9a-f][0-9a-f]-[0-9a-f]{32}-[0-9a-f]{16}-[0-9a-f][0-9a-f]$", traceparent);
                     Assert.Null(startRequest.Headers["tracestate"]);
                     Assert.Null(startRequest.Headers["Request-Id"]);
+
+                    KeyValuePair<string, object> stopEvent;
+                    Assert.True(eventRecords.Records.TryDequeue(out stopEvent));
+                    Assert.Equal("System.Net.Http.Desktop.HttpRequestOut.Stop", stopEvent.Key);
+                    HttpWebRequest stopRequest = ReadPublicProperty<HttpWebRequest>(stopEvent.Value, "Request");
+                    Assert.NotNull(stopRequest);
+
+                    HttpWebResponse stopResponse = ReadPublicProperty<HttpWebResponse>(stopEvent.Value, "Response");
+                    Assert.NotNull(stopResponse);
                 }
             }
             finally