TaskScheduler: Bump thread priority during shutdown.

base/task_scheduler/task_tracker.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/task_tracker.h"
 
 #include <limits>
 
 #include "base/atomicops.h"
 #include "base/callback.h"
@@ skipping 106 matching lines @@
 TaskTracker::TaskTracker() : state_(new State) {}
 TaskTracker::~TaskTracker() = default;
 
 void TaskTracker::Shutdown() {
   {
     AutoSchedulerLock auto_lock(shutdown_lock_);
 
     // This method can only be called once.
     DCHECK(!shutdown_event_);
     DCHECK(!num_block_shutdown_tasks_posted_during_shutdown_);
+    DCHECK(!state_->HasShutdownStarted());
 
     shutdown_event_.reset(
         new WaitableEvent(WaitableEvent::ResetPolicy::MANUAL,
                           WaitableEvent::InitialState::NOT_SIGNALED));
 
     const bool tasks_are_blocking_shutdown = state_->StartShutdown();
 
     // From now, if a thread causes the number of tasks blocking shutdown to
     // become zero, it will call OnBlockingShutdownTasksComplete().
 
@@ skipping 70 matching lines @@
 
     TRACE_TASK_EXECUTION(kRunFunctionName, *task);
 
     debug::TaskAnnotator task_annotator;
     task_annotator.RunTask(kQueueFunctionName, *task);
   }
 
   AfterRunTask(shutdown_behavior);
 }
 
+bool TaskTracker::HasShutdownStarted() const {
+  return state_->HasShutdownStarted();
+}
+
 bool TaskTracker::IsShutdownComplete() const {
   AutoSchedulerLock auto_lock(shutdown_lock_);
   return shutdown_event_ && shutdown_event_->IsSignaled();
 }
 
-bool TaskTracker::IsShuttingDownForTesting() const {
-  AutoSchedulerLock auto_lock(shutdown_lock_);
-  return shutdown_event_ && !shutdown_event_->IsSignaled();
+void TaskTracker::SetHasShutdownStartedForTesting() {
+  state_->StartShutdown();
 }
 
 bool TaskTracker::BeforePostTask(TaskShutdownBehavior shutdown_behavior) {
   if (shutdown_behavior == TaskShutdownBehavior::BLOCK_SHUTDOWN) {
     // BLOCK_SHUTDOWN tasks block shutdown between the moment they are posted
     // and the moment they complete their execution.
     const bool shutdown_started = state_->IncrementNumTasksBlockingShutdown();
 
     if (shutdown_started) {
       AutoSchedulerLock auto_lock(shutdown_lock_);
@@ skipping 83 matching lines @@
 
   // This method can only be called after shutdown has started.
   DCHECK(state_->HasShutdownStarted());
   DCHECK(shutdown_event_);
 
   shutdown_event_->Signal();
 }
 
 }  // namespace internal
 }  // namespace base