[Media Router] Fix shutdown hang on Windows firewall check.

This updates the task posted to check the Windows firewall settings to
CONTINUE_ON_SHUTDOWN, to fix a shutdown hang.

Bug: 902821
Change-Id: I4f261db1d08a075f39422f7c553394e2a95624ea
Reviewed-on: https://chromium-review.googlesource.com/c/1336915Reviewed-by: Brandon Tolsch <btolsch@chromium.org>
Commit-Queue: mark a. foltz <mfoltz@chromium.org>
Cr-Commit-Position: refs/heads/master@{#608469}

chrome/browser/media/router/mojo/media_route_provider_util_win.cc

@@ -9,6 +9,7 @@
 #include "base/logging.h"
 #include "base/path_service.h"
 #include "base/task/post_task.h"
+#include "base/task/task_traits.h"
 #include "base/task_runner_util.h"
 #include "chrome/installer/util/firewall_manager_win.h"
 
@@ -33,7 +34,8 @@ bool DoCanFirewallUseLocalPorts() {
 }  // namespace
 
 void CanFirewallUseLocalPorts(base::OnceCallback<void(bool)> callback) {
-  auto task_runner = base::CreateCOMSTATaskRunnerWithTraits({base::MayBlock()});
+  auto task_runner = base::CreateCOMSTATaskRunnerWithTraits(
+      {base::MayBlock(), base::TaskShutdownBehavior::CONTINUE_ON_SHUTDOWN});
   base::PostTaskAndReplyWithResult(task_runner.get(), FROM_HERE,
                                    base::BindOnce(&DoCanFirewallUseLocalPorts),
                                    std::move(callback));