Add TaskScheduler::JoinForTesting().

base/task_scheduler/scheduler_worker_pool_impl.h

 // 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.
 
 #ifndef BASE_TASK_SCHEDULER_SCHEDULER_WORKER_POOL_IMPL_H_
 #define BASE_TASK_SCHEDULER_SCHEDULER_WORKER_POOL_IMPL_H_
 
 #include <stddef.h>
 
 #include <memory>
@@ skipping 79 matching lines @@
 
   void GetHistograms(std::vector<const HistogramBase*>* histograms) const;
 
   // Waits until all workers are idle.
   void WaitForAllWorkersIdleForTesting();
 
   // Joins all workers of this worker pool. Tasks that are already running are
   // allowed to complete their execution. This can only be called once.
   void JoinForTesting();
 
-  // Disallows worker thread detachment. If the suggested reclaim time is not
-  // TimeDelta::Max(), then the test should call this before the detach code can
-  // run. The safest place to do this is before the a set of work is dispatched
-  // (the worker pool is idle and steady state) or before the last
-  // synchronization point for all workers (all threads are busy and can't be
-  // reclaimed).
+  // Disallows worker detachment. If the suggested reclaim time is not
+  // TimeDelta::Max(), the test must call this before JoinForTesting() to reduce
+  // the chance of thread detachment during the process of joining all of the
+  // threads, and as a result, threads running after JoinForTesting().
   void DisallowWorkerDetachmentForTesting();
 
   // Returns the number of workers alive in this worker pool. The value may
   // change if workers are woken up or detached during this call.
   size_t NumberOfAliveWorkersForTesting();
 
  private:
   class SchedulerSingleThreadTaskRunner;
   class SchedulerWorkerDelegateImpl;
 
@@ skipping 90 matching lines @@
   TaskTracker* const task_tracker_;
   DelayedTaskManager* const delayed_task_manager_;
 
   DISALLOW_COPY_AND_ASSIGN(SchedulerWorkerPoolImpl);
 };
 
 }  // namespace internal
 }  // namespace base
 
 #endif  // BASE_TASK_SCHEDULER_SCHEDULER_WORKER_POOL_IMPL_H_