Restore call's final stats collection in PC level framework

Bug: webrtc:11479
Change-Id: I763e13315250519f391e3c9dc0f36fe84569844f
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/173320
Commit-Queue: Artem Titov <titovartem@webrtc.org>
Reviewed-by: Mirko Bonadei <mbonadei@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#31040}

test/pc/e2e/peer_connection_quality_test.cc

@@ -317,6 +317,15 @@ void PeerConnectionE2EQualityTest::Run(RunParams run_params) {
   // Stop all client started tasks to prevent their access to any call related
   // objects after these objects will be destroyed during call tear down.
   executor_->Stop();
+  // There is no guarantee, that last stats collection will happen at the end
+  // of the call, so we force it after executor, which is among others is doing
+  // stats collection, was stopped.
+  task_queue_->SendTask(
+      [&stats_poller]() {
+        // Get final end-of-call stats.
+        stats_poller.PollStatsAndNotifyObservers();
+      },
+      RTC_FROM_HERE);
   // We need to detach AEC dumping from peers, because dump uses |task_queue_|
   // inside.
   alice_->DetachAecDump();