Remove the |max_threads| argument from CreateAndSetSimpleTaskScheduler().

base/task_scheduler/task_scheduler.cc

 // 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.
 
 #include "base/task_scheduler/task_scheduler.h"
 
+#include <algorithm>
+
 #include "base/bind.h"
 #include "base/logging.h"
+#include "base/sys_info.h"
 #include "base/task_scheduler/scheduler_worker_pool_params.h"
 #include "base/task_scheduler/task_scheduler_impl.h"
 #include "base/threading/platform_thread.h"
 #include "base/time/time.h"
 
 namespace base {
 
 namespace {
 
 // |g_task_scheduler| is intentionally leaked on shutdown.
 TaskScheduler* g_task_scheduler = nullptr;
 
 }  // namespace
 
 // static
-void TaskScheduler::CreateAndSetSimpleTaskScheduler(int max_threads) {
+void TaskScheduler::CreateAndSetSimpleTaskScheduler(const std::string& name) {
+  constexpr int kMinNumThreads = 2;

[robliao, 2017/03/13 23:56:05]

For single-core non-hyperthreaded processors, should this be 2?

[fdoray, 2017/03/14 15:08:22]

1 might be a more justifiable lower bound.

   std::vector<SchedulerWorkerPoolParams> worker_pool_params_vector;
   worker_pool_params_vector.emplace_back(
-      "Simple", ThreadPriority::NORMAL,
-      SchedulerWorkerPoolParams::StandbyThreadPolicy::LAZY, max_threads,
+      name, ThreadPriority::NORMAL,
+      SchedulerWorkerPoolParams::StandbyThreadPolicy::LAZY,
+      std::max(kMinNumThreads, base::SysInfo::NumberOfProcessors()),
       TimeDelta::FromSeconds(30));
   CreateAndSetDefaultTaskScheduler(
       worker_pool_params_vector,
       Bind([](const TaskTraits&) -> size_t { return 0; }));
 }
 
 // static
 void TaskScheduler::CreateAndSetDefaultTaskScheduler(
     const std::vector<SchedulerWorkerPoolParams>& worker_pool_params_vector,
     const WorkerPoolIndexForTraitsCallback&
         worker_pool_index_for_traits_callback) {
   SetInstance(internal::TaskSchedulerImpl::Create(
       worker_pool_params_vector, worker_pool_index_for_traits_callback));
 }
 
 // static
 void TaskScheduler::SetInstance(std::unique_ptr<TaskScheduler> task_scheduler) {
   delete g_task_scheduler;
   g_task_scheduler = task_scheduler.release();
 }
 
 // static
 TaskScheduler* TaskScheduler::GetInstance() {
   return g_task_scheduler;
 }
 
 }  // namespace base