[reference - do not submit] Always create four pools in TaskSchedulerImpl.

base/task_scheduler/scheduler_single_thread_task_runner_manager.h

Index: base/task_scheduler/scheduler_single_thread_task_runner_manager.h
diff --git a/base/task_scheduler/scheduler_single_thread_task_runner_manager.h b/base/task_scheduler/scheduler_single_thread_task_runner_manager.h
index 6fbad4bb1d0e7ef5a64a843a65c4118c48899b63..cf03165b64ac91bb19b65dfc34dc72f4af242614 100644
--- a/base/task_scheduler/scheduler_single_thread_task_runner_manager.h
+++ b/base/task_scheduler/scheduler_single_thread_task_runner_manager.h
@@ -5,6 +5,7 @@
 #ifndef BASE_TASK_SCHEDULER_SCHEDULER_SINGLE_THREAD_TASK_RUNNER_MANAGER_H_
 #define BASE_TASK_SCHEDULER_SCHEDULER_SINGLE_THREAD_TASK_RUNNER_MANAGER_H_
 
+#include <string>
 #include <vector>
 
 #include "base/atomicops.h"
@@ -13,8 +14,7 @@
 #include "base/macros.h"
 #include "base/memory/ref_counted.h"
 #include "base/task_scheduler/scheduler_lock.h"
-#include "base/task_scheduler/scheduler_worker_pool_params.h"
-#include "base/task_scheduler/task_scheduler.h"
+#include "base/threading/platform_thread.h"
 
 namespace base {
 
@@ -30,14 +30,17 @@ class TaskTracker;
 class BASE_EXPORT SchedulerSingleThreadTaskRunnerManager final {
  public:
   SchedulerSingleThreadTaskRunnerManager(
-      const std::vector<SchedulerWorkerPoolParams>& worker_pool_params_vector,
-      const TaskScheduler::WorkerPoolIndexForTraitsCallback&
-          worker_pool_index_for_traits_callback,
       TaskTracker* task_tracker,
       DelayedTaskManager* delayed_task_manager);
   ~SchedulerSingleThreadTaskRunnerManager();
 
+  // Create a SingleThreadTaskRunner which runs tasks with |traits| on a
+  // dedicated thread named "TaskScheduler" + |name| + "SingleThread" + index.
+  // |priority_hint| is the preferred thread priority; the actual thread
+  // priority depends on shutdown state and platform capabilities.
   scoped_refptr<SingleThreadTaskRunner> CreateSingleThreadTaskRunnerWithTraits(
+      const std::string& name,
+      ThreadPriority priority_hint,
       const TaskTraits& traits);
 
   void JoinForTesting();
@@ -46,13 +49,11 @@ class BASE_EXPORT SchedulerSingleThreadTaskRunnerManager final {
   class SchedulerSingleThreadTaskRunner;
 
   SchedulerWorker* CreateAndRegisterSchedulerWorker(
-      const SchedulerWorkerPoolParams& params);
+      const std::string& name,
+      ThreadPriority priority_hint);
 
   void UnregisterSchedulerWorker(SchedulerWorker* worker);
 
-  const std::vector<SchedulerWorkerPoolParams> worker_pool_params_vector_;
-  const TaskScheduler::WorkerPoolIndexForTraitsCallback
-      worker_pool_index_for_traits_callback_;
   TaskTracker* const task_tracker_;
   DelayedTaskManager* const delayed_task_manager_;