TaskScheduler [8] SEQUENCED TaskRunners in SchedulerThreadPool.

base/task_scheduler/scheduler_thread_pool.cc

Index: base/task_scheduler/scheduler_thread_pool.cc
diff --git a/base/task_scheduler/scheduler_thread_pool.cc b/base/task_scheduler/scheduler_thread_pool.cc
index ca9161c2029915d47ed5dcd527ca78b1bddf36a1..7509567b514905085dbbaf4596e5e46554b57eab 100644
--- a/base/task_scheduler/scheduler_thread_pool.cc
+++ b/base/task_scheduler/scheduler_thread_pool.cc
@@ -11,6 +11,7 @@
 #include "base/lazy_instance.h"
 #include "base/logging.h"
 #include "base/memory/ptr_util.h"
+#include "base/sequenced_task_runner.h"
 #include "base/task_scheduler/utils.h"
 #include "base/threading/thread_local.h"
 
@@ -63,6 +64,51 @@ class SchedulerParallelTaskRunner : public TaskRunner {
   DISALLOW_COPY_AND_ASSIGN(SchedulerParallelTaskRunner);
 };
 
+// A task runner that runs tasks with the SEQUENCED ExecutionMode.
+class SchedulerSequencedTaskRunner : public SequencedTaskRunner {
+ public:
+  SchedulerSequencedTaskRunner(const TaskTraits& traits,
+                               PriorityQueue* priority_queue,
+                               TaskTracker* task_tracker)
+      : traits_(traits),
+        priority_queue_(priority_queue),
+        task_tracker_(task_tracker) {}
+
+  // SequencedTaskRunner:
+  bool PostDelayedTask(const tracked_objects::Location& from_here,
+                       const Closure& closure,
+                       TimeDelta delay) override {
+    // TODO(fdoray): Support delayed tasks.
+    DCHECK(delay.is_zero());
+
+    return PostTaskHelper(WrapUnique(new Task(from_here, closure, traits_)),
+                          sequence_, priority_queue_, task_tracker_);
+  }
+
+  bool PostNonNestableDelayedTask(const tracked_objects::Location& from_here,
+                                  const Closure& closure,
+                                  base::TimeDelta delay) override {
+    // Tasks are never nested within the task scheduler.
+    return PostDelayedTask(from_here, closure, delay);
+  }
+
+  bool RunsTasksOnCurrentThread() const override {
+    return tls_current_shared_priority_queue.Get().Get() == priority_queue_;
+  }
+
+ private:
+  ~SchedulerSequencedTaskRunner() override = default;
+
+  // Sequence in which all Tasks posted through this TaskRunner are inserted.
+  const scoped_refptr<Sequence> sequence_ = new Sequence;
+
+  const TaskTraits traits_;
+  PriorityQueue* const priority_queue_;
+  TaskTracker* const task_tracker_;
+
+  DISALLOW_COPY_AND_ASSIGN(SchedulerSequencedTaskRunner);
+};
+
 }  // namespace
 
 std::unique_ptr<SchedulerThreadPool> SchedulerThreadPool::CreateThreadPool(
@@ -92,8 +138,11 @@ scoped_refptr<TaskRunner> SchedulerThreadPool::CreateTaskRunnerWithTraits(
           traits, &shared_priority_queue_, task_tracker_));
 
     case ExecutionMode::SEQUENCED:
+      return make_scoped_refptr(new SchedulerSequencedTaskRunner(
+          traits, &shared_priority_queue_, task_tracker_));
+
     case ExecutionMode::SINGLE_THREADED:
-      // TODO(fdoray): Support SEQUENCED and SINGLE_THREADED TaskRunners.
+      // TODO(fdoray): Support SINGLE_THREADED TaskRunners.
       NOTREACHED();
       return nullptr;
   }