Browser WBT on Chrome: avoid "no such window: target window already closed" (#1265)

* Avoid "no such window: target window already closed" exception.

* Give the browser 1 sec before re-checking if `driverService` is finished.

* Feedback, allow delay cancellation.

Author: ilonatommy

src/Microsoft.DotNet.XHarness.CLI/Commands/WASM/Browser/WasmTestBrowserCommand.cs

@@ -127,9 +127,10 @@ protected override async Task<ExitCode> InvokeInternal(ILogger logger)
                         driver.SwitchTo().Window(lastWindowHandle);
                     }
                 }
+                await Task.Delay(TimeSpan.FromSeconds(1), cts.Token);
                 if (driverService.IsRunning)
                 {
-                    if (!cts.IsCancellationRequested)
+                    if (!cts.IsCancellationRequested && driver.WindowHandles.Count != 0)
                     {
                         driver.Navigate().GoToUrl("about:config");
                         driver.Navigate().GoToUrl("about:blank");