Flush TaskScheduler in content::RunAllBlockingPoolTasksUntilIdle().

base/test/scoped_task_scheduler.cc

 // Copyright 2016 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_task_scheduler.h"
 
 #include <memory>
 #include <utility>
 #include <vector>
 
@@ skipping 170 matching lines @@
 void TestTaskScheduler::Shutdown() {
   // Prevent SKIP_ON_SHUTDOWN and CONTINUE_ON_SHUTDOWN tasks from running from
   // now on.
   task_tracker_.SetHasShutdownStartedForTesting();
 
   // Run pending BLOCK_SHUTDOWN tasks.
   RunLoop().RunUntilIdle();
 }
 
 void TestTaskScheduler::FlushForTesting() {
-  NOTREACHED();
+  RunLoop().RunUntilIdle();
 }
 
 void TestTaskScheduler::JoinForTesting() {
   // TestTaskScheduler doesn't create threads so this does nothing.
 }
 
 bool TestTaskScheduler::PostTask(std::unique_ptr<internal::Task> task,
                                  const SequenceToken& sequence_token) {
   DCHECK(task);
   if (!task_tracker_.WillPostTask(task.get()))
@@ skipping 85 matching lines @@
   DCHECK_EQ(task_scheduler_, TaskScheduler::GetInstance());
 
   // Per contract, call JoinForTesting() before deleting the TaskScheduler.
   TaskScheduler::GetInstance()->JoinForTesting();
 
   TaskScheduler::SetInstance(nullptr);
 }
 
 }  // namespace test
 }  // namespace base