Separate the create and start phases in TaskSchedulerImpl.

base/task_scheduler/scheduler_worker_pool_impl.h

 // 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.
 
 #ifndef BASE_TASK_SCHEDULER_SCHEDULER_WORKER_POOL_IMPL_H_
 #define BASE_TASK_SCHEDULER_SCHEDULER_WORKER_POOL_IMPL_H_
 
 #include <stddef.h>
 
 #include <memory>
@@ skipping 20 matching lines @@
 
 class HistogramBase;
 class SchedulerWorkerPoolParams;
 class TaskTraits;
 
 namespace internal {
 
 class DelayedTaskManager;
 class TaskTracker;
 
-// A pool of workers that run Tasks. This class is thread-safe.
+// A pool of workers that run Tasks.
+//
+// The pool doesn't create threads until Start() is called. Tasks can be posted
+// at any time but will not run until after Start() is called.
+//
+// This class is thread-safe.
 class BASE_EXPORT SchedulerWorkerPoolImpl : public SchedulerWorkerPool {
  public:
   // Callback invoked when a Sequence isn't empty after a worker pops a Task
   // from it.
   using ReEnqueueSequenceCallback = Callback<void(scoped_refptr<Sequence>)>;
 
-  // Constructs a pool without workers. Tasks can be posted to the pool, but
-  // they won't run until workers are created. To create workers and start
-  // running tasks, call Start().
+  // Constructs a pool without workers.
   //
   // |name| is used to label the pool's threads ("TaskScheduler" + |name| +
   // index) and histograms ("TaskScheduler." + histogram name + "." + |name| +
   // extra suffixes). |priority_hint| is the preferred thread priority; the
   // actual thread priority depends on shutdown state and platform capabilities.
   // |re_enqueue_sequence_callback| is invoked when a Sequence isn't empty after
   // a worker pops a Task from it. |task_tracker| keeps track of tasks.
   // |delayed_task_manager| handles tasks posted with a delay.
   SchedulerWorkerPoolImpl(
       const std::string& name,
@@ skipping 143 matching lines @@
   TaskTracker* const task_tracker_;
   DelayedTaskManager* const delayed_task_manager_;
 
   DISALLOW_COPY_AND_ASSIGN(SchedulerWorkerPoolImpl);
 };
 
 }  // namespace internal
 }  // namespace base
 
 #endif  // BASE_TASK_SCHEDULER_SCHEDULER_WORKER_POOL_IMPL_H_