scheduler: Don't run multiple tasks per batch in a nested run loop

components/scheduler/child/task_queue_manager.cc

Index: components/scheduler/child/task_queue_manager.cc
diff --git a/components/scheduler/child/task_queue_manager.cc b/components/scheduler/child/task_queue_manager.cc
index 5f06d6a7fe98298be636e572ff14068acad98f60..55bd4f74d7eab2af51214e93b185530a32b2046d 100644
--- a/components/scheduler/child/task_queue_manager.cc
+++ b/components/scheduler/child/task_queue_manager.cc
@@ -155,6 +155,11 @@ void TaskQueueManager::DoWork(bool posted_from_main_thread) {
                                  TaskQueue::WakeupPolicy::CAN_WAKE_OTHER_QUEUES;
     if (!UpdateWorkQueues(should_trigger_wakeup, &previous_task))
       return;
+
+    // Only run a single task per batch in nested run loops so that we can
+    // properly exit the nested loop when someone calls RunLoop::Quit().
+    if (main_task_runner_->IsNested())
+      break;
   }
 }