TaskScheduler: Set the current SequenceToken when a Task runs.

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"
 #include "base/debug/task_annotator.h"
 #include "base/logging.h"
 #include "base/metrics/histogram_macros.h"
+#include "base/sequence_token.h"
 #include "base/threading/sequenced_task_runner_handle.h"
 #include "base/threading/thread_restrictions.h"
 #include "base/threading/thread_task_runner_handle.h"
 #include "base/trace_event/trace_event.h"
 
 namespace base {
 namespace internal {
 
 namespace {
 
@@ skipping 145 matching lines @@
 
   if (!BeforePostTask(task->traits.shutdown_behavior()))
     return false;
 
   debug::TaskAnnotator task_annotator;
   task_annotator.DidQueueTask(kQueueFunctionName, *task);
 
   return true;
 }
 
-void TaskTracker::RunTask(const Task* task) {
-  DCHECK(task);
+void TaskTracker::RunNextTaskInSequence(const Sequence* sequence) {
+  DCHECK(sequence);
+  DCHECK(sequence->PeekTask());
+
+  const Task* task = sequence->PeekTask();
 
   const TaskShutdownBehavior shutdown_behavior =
       task->traits.shutdown_behavior();
   if (!BeforeRunTask(shutdown_behavior))
     return;
 
   // All tasks run through here and the scheduler itself doesn't use singletons.
   // Therefore, it isn't necessary to reset the singleton allowed bit after
   // running the task.
   ThreadRestrictions::SetSingletonAllowed(
       task->traits.shutdown_behavior() !=
       TaskShutdownBehavior::CONTINUE_ON_SHUTDOWN);
 
   {
+    // Set up SequenceToken as expected for the scope of the task.
+    ScopedSetCurrentSequenceToken scoped_set_current_sequence_token(
+        sequence->token());
+
     // Set up TaskRunnerHandle as expected for the scope of the task.
     std::unique_ptr<SequencedTaskRunnerHandle> sequenced_task_runner_handle;
     std::unique_ptr<ThreadTaskRunnerHandle> single_thread_task_runner_handle;
     DCHECK(!task->sequenced_task_runner_ref ||
            !task->single_thread_task_runner_ref);
     if (task->sequenced_task_runner_ref) {
       sequenced_task_runner_handle.reset(
           new SequencedTaskRunnerHandle(task->sequenced_task_runner_ref));
     } else if (task->single_thread_task_runner_ref) {
       single_thread_task_runner_handle.reset(
@@ skipping 113 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