Move code that sets up the environment to run a task to TaskTracker::PerformRunTask().

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/atomicops.h"
@@ skipping 59 matching lines @@
 
   // Returns true if shutdown has completed (Shutdown() has returned).
   bool IsShutdownComplete() 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();
 
  protected:
-  // Runs |task|. An override is expected to call its parent's implementation
-  // but is free to perform extra work before and after doing so.
-  virtual void PerformRunTask(std::unique_ptr<Task> task);
+  // Runs |task|. |sequence_token| is the token identifying the sequence from
+  // which |task| was extracted. An override is expected to call its parent's
+  // implementation but is free to perform extra work before and after doing so.
+  virtual void PerformRunTask(std::unique_ptr<Task> task,
+                              const SequenceToken& sequence_token);
 
 #if DCHECK_IS_ON()
   // Returns true if this context should be exempt from blocking shutdown
   // DCHECKs.
   // TODO(robliao): Remove when http://crbug.com/698140 is fixed.
   virtual bool IsPostingBlockShutdownTaskAfterShutdownAllowed();
 #endif
 
  private:
   class State;
@@ skipping 63 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_