TaskScheduler [12] Support SINGLE_THREADED in SchedulerThreadPool DO NOT SUBMIT

base/task_scheduler/scheduler_worker_thread.h

Index: base/task_scheduler/scheduler_worker_thread.h
diff --git a/base/task_scheduler/scheduler_worker_thread.h b/base/task_scheduler/scheduler_worker_thread.h
index 6721309180ca56ae0fdb26b4cff7a6989f77b3e9..f0b03d18296348ed6cdf97cadc8437591e65045a 100644
--- a/base/task_scheduler/scheduler_worker_thread.h
+++ b/base/task_scheduler/scheduler_worker_thread.h
@@ -7,6 +7,7 @@
 
 #include <memory>
 
+#include "base/atomicops.h"
 #include "base/base_export.h"
 #include "base/macros.h"
 #include "base/memory/ref_counted.h"
@@ -83,6 +84,10 @@ class BASE_EXPORT SchedulerWorkerThread : public PlatformThread::Delegate,
   scoped_refptr<SingleThreadTaskRunner> CreateTaskRunnerWithTraits(
       const TaskTraits& traits);
 
+  // Returns the number of single-thread TaskRunners associated with this
+  // SchedulerWorkerThread.
+  size_t GetNumSingleThreadTaskRunners() const;
+
   // Wakes up this SchedulerWorkerThread if it wasn't already awake. After this
   // is called, this SchedulerWorkerThread will run Tasks from Sequences
   // returned by the GetWork() method of its delegate until it returns nullptr.
@@ -114,6 +119,10 @@ class BASE_EXPORT SchedulerWorkerThread : public PlatformThread::Delegate,
   // Event signaled to wake up this SchedulerWorkerThread.
   WaitableEvent wake_up_event_;
 
+  // Number of single-thread TaskRunners associated with this
+  // SchedulerWorkerThread.
+  base::subtle::Atomic32 num_single_thread_task_runners_;
+
   // PriorityQueue for Tasks/Sequences posted through SingleThreadTaskRunners
   // returned by CreateTaskRunnerWithTraits.
   PriorityQueue single_threaded_priority_queue_;