TaskScheduler: Remove base::ExecutionMode.

base/task_scheduler/task_scheduler.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_SCHEDULER_H_
 #define BASE_TASK_SCHEDULER_TASK_SCHEDULER_H_
 
 #include <memory>
 #include <vector>
 
 #include "base/base_export.h"
 #include "base/callback_forward.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/task_traits.h"
 
 namespace tracked_objects {
 class Location;
 }
 
 namespace base {
 
 class HistogramBase;
@@ skipping 12 matching lines @@
       Callback<size_t(const TaskTraits& traits)>;
 
   virtual ~TaskScheduler() = default;
 
   // Posts |task| with specific |traits|.
   // For one off tasks that don't require a TaskRunner.
   virtual void PostTaskWithTraits(const tracked_objects::Location& from_here,
                                   const TaskTraits& traits,
                                   const Closure& task) = 0;
 
-  // Returns a TaskRunner whose PostTask invocations will result in scheduling
-  // Tasks with |traits| which will be executed according to |execution_mode|.
+  // Returns a TaskRunner whose PostTask invocations result in scheduling tasks
+  // 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 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 using |traits|. Tasks run on a single thread in posting
+  // order.
+  virtual scoped_refptr<SingleThreadTaskRunner>
+  CreateSingleThreadTaskRunnerWithTraits(const TaskTraits& traits) = 0;
 
   // Returns a vector of all histograms available in this task scheduler.
   virtual std::vector<const HistogramBase*> GetHistograms() const = 0;
 
   // Synchronously shuts down the scheduler. Once this is called, only tasks
   // posted with the BLOCK_SHUTDOWN behavior will be run. When this returns:
   // - All SKIP_ON_SHUTDOWN tasks that were already running have completed their
   //   execution.
   // - All posted BLOCK_SHUTDOWN tasks have completed their execution.
   // - CONTINUE_ON_SHUTDOWN tasks might still be running.
@@ skipping 32 matching lines @@
 
   // Retrieve the TaskScheduler set via CreateAndSetDefaultTaskScheduler() or
   // SetInstance(). This should be used very rarely; most users of TaskScheduler
   // should use the post_task.h API.
   static TaskScheduler* GetInstance();
 };
 
 }  // namespace base
 
 #endif  // BASE_TASK_SCHEDULER_TASK_SCHEDULER_H_