perf: Use CONTINUE_ON_SHUTDOWN task runner to avoid shutdown hang

BUG=840743

Change-Id: Ie220fcaaad0204e23dbcc1c935e0aad8c7d0b88f
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1772848
Reviewed-by: Gabriel Marin <gmx@chromium.org>
Commit-Queue: Ryo Hashimoto <hashimoto@chromium.org>
Cr-Commit-Position: refs/heads/master@{#691472}

chrome/browser/metrics/perf/perf_output.cc

@@ -21,9 +21,11 @@ PerfOutputCall::PerfOutputCall(base::TimeDelta duration,
       pending_stop_(false) {
   DCHECK_CALLED_ON_VALID_THREAD(thread_checker_);
 
-  perf_data_pipe_reader_ = std::make_unique<chromeos::PipeReader>(
-      base::CreateTaskRunner({base::ThreadPool(), base::MayBlock(),
-                              base::TaskPriority::USER_VISIBLE}));
+  perf_data_pipe_reader_ =
+      std::make_unique<chromeos::PipeReader>(base::CreateTaskRunner(
+          {base::ThreadPool(), base::MayBlock(),
+           base::TaskPriority::USER_VISIBLE,
+           base::TaskShutdownBehavior::CONTINUE_ON_SHUTDOWN}));
 
   base::ScopedFD pipe_write_end =
       perf_data_pipe_reader_->StartIO(base::BindOnce(