Move Task Scheduler Single Thread Task Runners to Dedicated Threads

base/task_scheduler/scheduler_worker_pool_impl.h

Index: base/task_scheduler/scheduler_worker_pool_impl.h
diff --git a/base/task_scheduler/scheduler_worker_pool_impl.h b/base/task_scheduler/scheduler_worker_pool_impl.h
index 3205dae7d1a25d6a0034ba11cc6d7f0ca9562f02..0dd16bf433f51d378ad783ecf0c0216da0e5c7bb 100644
--- a/base/task_scheduler/scheduler_worker_pool_impl.h
+++ b/base/task_scheduler/scheduler_worker_pool_impl.h
@@ -45,6 +45,10 @@ class BASE_EXPORT SchedulerWorkerPoolImpl : public SchedulerWorkerPool {
   // from it.
   using ReEnqueueSequenceCallback = Callback<void(scoped_refptr<Sequence>)>;
 
+  // Callback invoked during destruction of a SingleThreadTaskRunner.
+  using UnregisterSingleThreadWorkerPoolCallback =
+      Callback<void(const SchedulerWorkerPoolImpl* scheduler_worker_pool)>;
+
   // Destroying a SchedulerWorkerPoolImpl returned by Create() is not allowed in
   // production; it is always leaked. In tests, it can only be destroyed after
   // JoinForTesting() has returned.
@@ -62,6 +66,13 @@ class BASE_EXPORT SchedulerWorkerPoolImpl : public SchedulerWorkerPool {
       TaskTracker* task_tracker,
       DelayedTaskManager* delayed_task_manager);
 
+  static std::unique_ptr<SchedulerWorkerPoolImpl> CreateSingleThreadWorkerPool(
+      const SchedulerWorkerPoolParams& params,
+      UnregisterSingleThreadWorkerPoolCallback
+          unregister_single_thread_worker_callback,
+      TaskTracker* task_tracker,
+      DelayedTaskManager* delayed_task_manager);
+
   // SchedulerWorkerPool:
   scoped_refptr<TaskRunner> CreateTaskRunnerWithTraits(
       const TaskTraits& traits) override;
@@ -112,6 +123,11 @@ class BASE_EXPORT SchedulerWorkerPoolImpl : public SchedulerWorkerPool {
   SchedulerWorkerPoolImpl(const SchedulerWorkerPoolParams& params,
                           TaskTracker* task_tracker,
                           DelayedTaskManager* delayed_task_manager);
+  SchedulerWorkerPoolImpl(const SchedulerWorkerPoolParams& params,
+                          TaskTracker* task_tracker,
+                          DelayedTaskManager* delayed_task_manager,
+                          UnregisterSingleThreadWorkerPoolCallback

[fdoray, 2017/01/27 16:47:35]

Move after |params| to keep the same order as CreateSingleThreadWorkerPool().

[robliao, 2017/01/27 21:25:41]

The reason this is at the end is the previous constructor has the same set at
the beginning. It's a loose convention to keep the constructor argument order
consistent and add additional parameters at the end for overloading purposes.

Now that I look at this again, C++ default arguments can handle this case, so
I've gone with that.

+                              unregister_single_thread_worker_pool_callback);
 
   bool Initialize(
       const SchedulerWorkerPoolParams& params,
@@ -199,6 +215,9 @@ class BASE_EXPORT SchedulerWorkerPoolImpl : public SchedulerWorkerPool {
   TaskTracker* const task_tracker_;
   DelayedTaskManager* const delayed_task_manager_;
 
+  const UnregisterSingleThreadWorkerPoolCallback
+      unregister_single_thread_worker_pool_callback_;
+
   DISALLOW_COPY_AND_ASSIGN(SchedulerWorkerPoolImpl);
 };