TaskScheduler: Bump thread priority during shutdown.

base/task_scheduler/task_tracker.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_TASK_TRACKER_H_
 #define BASE_TASK_SCHEDULER_TASK_TRACKER_H_
 
 #include <memory>
 
 #include "base/base_export.h"
@@ skipping 26 matching lines @@
   void Shutdown();
 
   // Informs this TaskTracker that |task| is about to be posted. Returns true if
   // this operation is allowed (|task| should be posted if-and-only-if it is).
   bool WillPostTask(const Task* task);
 
   // Runs |task| unless the current shutdown state prevents that. WillPostTask()
   // must have allowed |task| to be posted.
   void RunTask(const Task* task);
 
-  // Returns true if shutdown has completed.
+  // Returns true once shutdown has started (Shutdown() has been called but
+  // might not have returned).
+  bool HasShutdownStarted() const;
+
+  // Returns true if shutdown has completed (Shutdown() has returned).
   bool IsShutdownComplete() const;
 
-  // Returns true while shutdown is in progress (i.e. Shutdown() has been called
-  // but hasn't returned).
-  bool IsShuttingDownForTesting() const;
+  // Causes HasShutdownStarted() to return true. Unlike when Shutdown() returns,
+  // IsShutdownComplete() won't return true after this returns. Shutdown()
+  // cannot be called after this.
+  void SetHasShutdownStartedForTesting();
 
  private:
   class State;
 
   // Called before WillPostTask() informs the tracing system that a task has
   // been posted. Updates |num_tasks_blocking_shutdown_| if necessary and
   // returns true if the current shutdown state allows the task to be posted.
   bool BeforePostTask(TaskShutdownBehavior shutdown_behavior);
 
   // Called before a task with |shutdown_behavior| is run by RunTask(). Updates
@@ skipping 24 matching lines @@
   // Number of BLOCK_SHUTDOWN tasks posted during shutdown.
   HistogramBase::Sample num_block_shutdown_tasks_posted_during_shutdown_ = 0;
 
   DISALLOW_COPY_AND_ASSIGN(TaskTracker);
 };
 
 }  // namespace internal
 }  // namespace base
 
 #endif  // BASE_TASK_SCHEDULER_TASK_TRACKER_H_