Flush TaskScheduler in ~ScopedTaskEnvironment and ~ScopedAsyncTaskScheduler.

base/test/scoped_async_task_scheduler.cc

 // Copyright 2017 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "base/test/scoped_async_task_scheduler.h"
 
 #include "base/logging.h"
 #include "base/task_scheduler/scheduler_worker_pool_params.h"
 #include "base/task_scheduler/task_scheduler.h"
 
@@ skipping 11 matching lines @@
       SchedulerWorkerPoolParams::StandbyThreadPolicy::ONE, kMaxThreads,
       kSuggestedReclaimTime);
   TaskScheduler::CreateAndSetDefaultTaskScheduler(
       "ScopedAsync", {worker_pool_params, worker_pool_params,
                       worker_pool_params, worker_pool_params});
   task_scheduler_ = TaskScheduler::GetInstance();
 }
 
 ScopedAsyncTaskScheduler::~ScopedAsyncTaskScheduler() {
   DCHECK_EQ(TaskScheduler::GetInstance(), task_scheduler_);
+  // Without FlushForTesting(), DeleteSoon() and ReleaseSoon() tasks could be
+  // skipped, resulting in memory leaks.
+  TaskScheduler::GetInstance()->FlushForTesting();
   TaskScheduler::GetInstance()->Shutdown();
   TaskScheduler::GetInstance()->JoinForTesting();
   TaskScheduler::SetInstance(nullptr);
 }
 
 }  // namespace test
 }  // namespace base