src: discard remaining foreground tasks on platform shutdown

While V8 itself should not have any remaining tasks on the queue
during platform shutdown, our inspector implementation may do so.
Thus, the checks verifying that no tasks are queued at that point
make some of the inspector tasks flaky.
Remove the checks and replace them by explicitly destroying all
tasks that are left.

Refs: #25653
Refs: #28870 (comment)

PR-URL: #29587
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: David Carlier <devnexen@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Eugene Ostroukhov <eostroukhov@google.com>
Reviewed-By: Minwoo Jung <minwoo@nodesource.com>

Author: addaleax

src/node_platform.cc

@@ -279,8 +279,13 @@ void PerIsolatePlatformData::Shutdown() {
   if (flush_tasks_ == nullptr)
     return;
 
-  CHECK_NULL(foreground_delayed_tasks_.Pop());
-  CHECK_NULL(foreground_tasks_.Pop());
+  // While there should be no V8 tasks in the queues at this point, it is
+  // possible that Node.js-internal tasks from e.g. the inspector are still
+  // lying around. We clear these queues and ignore the return value,
+  // effectively deleting the tasks instead of running them.
+  foreground_delayed_tasks_.PopAll();
+  foreground_tasks_.PopAll();
+
   CancelPendingDelayedTasks();
 
   ShutdownCbList* copy = new ShutdownCbList(std::move(shutdown_callbacks_));