TaskScheduler: Remove OnMainExit from SchedulerWorkerThread::Delegate.

base/task_scheduler/scheduler_worker_thread.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/task_scheduler/scheduler_worker_thread.h"
 
 #include <stddef.h>
 
 #include <utility>
 
@@ skipping 74 matching lines @@
     if (!sequence_became_empty)
       delegate_->EnqueueSequence(std::move(sequence));
 
     // Calling WakeUp() guarantees that this SchedulerWorkerThread will run
     // Tasks from Sequences returned by the GetWork() method of |delegate_|
     // until it returns nullptr. Resetting |wake_up_event_| here doesn't break
     // this invariant and avoids a useless loop iteration before going to sleep
     // if WakeUp() is called while this SchedulerWorkerThread is awake.
     wake_up_event_.Reset();
   }
-
-  delegate_->OnMainExit();
 }
 
 bool SchedulerWorkerThread::ShouldExitForTesting() const {
   AutoSchedulerLock auto_lock(should_exit_for_testing_lock_);
   return should_exit_for_testing_;
 }
 
 }  // namespace internal
 }  // namespace base