Introduce SingleThreadTaskRunnerThreadMode

base/task_scheduler/task_scheduler_impl.h

Index: base/task_scheduler/task_scheduler_impl.h
diff --git a/base/task_scheduler/task_scheduler_impl.h b/base/task_scheduler/task_scheduler_impl.h
index 1307573ef0479453914e15ce87c1574407d33500..27458a4166c2a59e4065a9d0fd95e97c6d852bf0 100644
--- a/base/task_scheduler/task_scheduler_impl.h
+++ b/base/task_scheduler/task_scheduler_impl.h
@@ -53,10 +53,12 @@ class BASE_EXPORT TaskSchedulerImpl : public TaskScheduler {
   scoped_refptr<SequencedTaskRunner> CreateSequencedTaskRunnerWithTraits(
       const TaskTraits& traits) override;
   scoped_refptr<SingleThreadTaskRunner> CreateSingleThreadTaskRunnerWithTraits(
-      const TaskTraits& traits) override;
+      const TaskTraits& traits,
+      SingleThreadTaskRunnerThreadMode thread_mode) override;
 #if defined(OS_WIN)
   scoped_refptr<SingleThreadTaskRunner> CreateCOMSTATaskRunnerWithTraits(
-      const TaskTraits& traits) override;
+      const TaskTraits& traits,
+      SingleThreadTaskRunnerThreadMode thread_mode) override;
 #endif  // defined(OS_WIN)
   std::vector<const HistogramBase*> GetHistograms() const override;
   int GetMaxConcurrentTasksWithTraitsDeprecated(