TaskScheduler: Set the current SequenceToken when a Task runs.

base/task_scheduler/task_tracker.h

Index: base/task_scheduler/task_tracker.h
diff --git a/base/task_scheduler/task_tracker.h b/base/task_scheduler/task_tracker.h
index 609edbc07f35f068173ef643c8684e1226b4230c..80cc3c02870685ac421f4bb8f4278c376355e091 100644
--- a/base/task_scheduler/task_tracker.h
+++ b/base/task_scheduler/task_tracker.h
@@ -13,6 +13,7 @@
 #include "base/metrics/histogram_base.h"
 #include "base/synchronization/waitable_event.h"
 #include "base/task_scheduler/scheduler_lock.h"
+#include "base/task_scheduler/sequence.h"
 #include "base/task_scheduler/task.h"
 #include "base/task_scheduler/task_traits.h"
 
@@ -40,9 +41,9 @@ class BASE_EXPORT TaskTracker {
   // 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);
+  // Runs the next Task in |sequence| unless the current shutdown state prevents
+  // that. WillPostTask() must have allowed the Task to be posted.
+  void RunNextTaskInSequence(const Sequence* sequence);
 
   // Returns true once shutdown has started (Shutdown() has been called but
   // might not have returned).