message: Simplify stats poller stop in PC level framework
  Cr-Commit-Position: refs/heads/master@{#28876}
diff: @@ -51,7 +51,6 @@ constexpr int kFrameworkUsedThreads = 2;
  constexpr int kMaxVideoAnalyzerThreads = 8;
  constexpr TimeDelta kStatsUpdateInterval = TimeDelta::Seconds<1>();
  -constexpr TimeDelta kStatsPollingStopTimeout = TimeDelta::Seconds<1>();
  constexpr TimeDelta kAliveMessageLogInterval = TimeDelta::Seconds<30>();
  @@ -367,15 +366,10 @@ void PeerConnectionE2EQualityTest::Run(RunParams run_params) {
  done.Wait(run_params.run_duration.ms());
  }
  - rtc::Event stats_polling_stopped;
  - task_queue_->PostTask([&stats_polling_stopped, this]() {
  + task_queue_->SendTask([this]() {
  RTC_DCHECK_RUN_ON(task_queue_.get());
  stats_polling_task_.Stop();
  - stats_polling_stopped.Set();
  });
  - bool no_timeout = stats_polling_stopped.Wait(kStatsPollingStopTimeout.ms());
  - RTC_CHECK(no_timeout) << "Failed to stop Stats polling after "
  - << kStatsPollingStopTimeout.seconds() << " seconds.";
  // We need to detach AEC dumping from peers, because dump uses |task_queue_|
  // inside.
  