TaskScheduler: Remove base::ExecutionMode.

base/task_scheduler/scheduler_worker_pool.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_SCHEDULER_WORKER_POOL_H_
 #define BASE_TASK_SCHEDULER_SCHEDULER_WORKER_POOL_H_
 
 #include <memory>
 
 #include "base/base_export.h"
 #include "base/memory/ref_counted.h"
+#include "base/sequenced_task_runner.h"
+#include "base/single_thread_task_runner.h"
 #include "base/task_runner.h"
 #include "base/task_scheduler/sequence.h"
 #include "base/task_scheduler/task.h"
 #include "base/task_scheduler/task_traits.h"
 
 namespace base {
 namespace internal {
 
 class SchedulerWorker;
 class SequenceSortKey;
 
 // Interface for a worker pool.
 class BASE_EXPORT SchedulerWorkerPool {
  public:
   virtual ~SchedulerWorkerPool() = default;
 
-  // Returns a TaskRunner whose PostTask invocations will result in scheduling
-  // Tasks with |traits| and |execution_mode| in this SchedulerWorkerPool.
+  // Returns a TaskRunner whose PostTask invocations result in scheduling tasks
+  // in this SchedulerWorkerPool using |traits|. Tasks may run in any order and
+  // in parallel.
   virtual scoped_refptr<TaskRunner> CreateTaskRunnerWithTraits(
-      const TaskTraits& traits,
-      ExecutionMode execution_mode) = 0;
+      const TaskTraits& traits) = 0;
+
+  // Returns a SequencedTaskRunner whose PostTask invocations result in
+  // scheduling tasks in this SchedulerWorkerPool using |traits|. Tasks run one
+  // at a time in posting order.
+  virtual scoped_refptr<SequencedTaskRunner>
+  CreateSequencedTaskRunnerWithTraits(const TaskTraits& traits) = 0;
+
+  // Returns a SingleThreadTaskRunner whose PostTask invocations result in
+  // scheduling tasks in this SchedulerWorkerPool using |traits|. Tasks run on a
+  // single thread in posting order.
+  virtual scoped_refptr<SingleThreadTaskRunner>
+  CreateSingleThreadTaskRunnerWithTraits(const TaskTraits& traits) = 0;
 
   // Inserts |sequence| with |sequence_sort_key| into a queue of Sequences that
   // can be processed by any worker owned by this SchedulerWorkerPool. Must only
   // be used to put |sequence| back into a queue after running a Task from it.
   // The thread that calls this doesn't have to belong to this
   // SchedulerWorkerPool.
   virtual void ReEnqueueSequence(scoped_refptr<Sequence> sequence,
                                  const SequenceSortKey& sequence_sort_key) = 0;
 
   // Posts |task| to be executed by this SchedulerWorkerPool as part of
@@ skipping 14 matching lines @@
   // |task|'s delayed run time.
   virtual void PostTaskWithSequenceNow(std::unique_ptr<Task> task,
                                        scoped_refptr<Sequence> sequence,
                                        SchedulerWorker* worker) = 0;
 };
 
 }  // namespace internal
 }  // namespace base
 
 #endif  // BASE_TASK_SCHEDULER_SCHEDULER_WORKER_POOL_H_