Separate the create and start phases in TaskSchedulerImpl.

base/task_scheduler/task_scheduler_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_TASK_SCHEDULER_IMPL_H_
 #define BASE_TASK_SCHEDULER_TASK_SCHEDULER_IMPL_H_
 
 #include <memory>
 #include <vector>
 
@@ skipping 20 matching lines @@
 
 namespace base {
 
 class HistogramBase;
 
 namespace internal {
 
 // Default TaskScheduler implementation. This class is thread-safe.
 class BASE_EXPORT TaskSchedulerImpl : public TaskScheduler {
  public:
-  // Creates and returns an initialized TaskSchedulerImpl. CHECKs on failure.
-  // |name| is used to label threads and histograms. It should identify the
-  // component that creates the TaskScheduler. |init_params| contains params to
-  // initialize worker pools.
-  static std::unique_ptr<TaskSchedulerImpl> Create(
-      StringPiece name,
-      const TaskScheduler::InitParams& init_params);
-
+  explicit TaskSchedulerImpl(StringPiece name);

[robliao, 2017/04/24 22:32:19]

Readd the comment for |name| for public consistency.

[gab, 2017/04/25 15:16:15]

Also mention explicitly that it now must be started (so that users of //base
from outside of chrome using this to SetInstance() know when rolling passed this
change that there's an extra step to fix).

[fdoray, 2017/04/25 18:43:34]

Done.
I'd like to avoid duplicating the meta comment from the base class.

   ~TaskSchedulerImpl() override;
 
   // TaskScheduler:
+  void Start(const TaskScheduler::InitParams& init_params) override;
   void PostDelayedTaskWithTraits(const tracked_objects::Location& from_here,
                                  const TaskTraits& traits,
                                  OnceClosure task,
                                  TimeDelta delay) override;
   scoped_refptr<TaskRunner> CreateTaskRunnerWithTraits(
       const TaskTraits& traits) override;
   scoped_refptr<SequencedTaskRunner> CreateSequencedTaskRunnerWithTraits(
       const TaskTraits& traits) override;
   scoped_refptr<SingleThreadTaskRunner> CreateSingleThreadTaskRunnerWithTraits(
       const TaskTraits& traits) override;
 #if defined(OS_WIN)
   scoped_refptr<SingleThreadTaskRunner> CreateCOMSTATaskRunnerWithTraits(
       const TaskTraits& traits) override;
 #endif  // defined(OS_WIN)
   std::vector<const HistogramBase*> GetHistograms() const override;
   int GetMaxConcurrentTasksWithTraitsDeprecated(
       const TaskTraits& traits) const override;
   void Shutdown() override;
   void FlushForTesting() override;
   void JoinForTesting() override;
 
  private:
-  explicit TaskSchedulerImpl(StringPiece name);
-
-  void Initialize(const TaskScheduler::InitParams& init_params);
-
   // Returns the worker pool that runs Tasks with |traits|.
   SchedulerWorkerPoolImpl* GetWorkerPoolForTraits(
       const TaskTraits& traits) const;
 
   // Callback invoked when a non-single-thread |sequence| isn't empty after a
   // worker pops a Task from it.
   void ReEnqueueSequenceCallback(scoped_refptr<Sequence> sequence);
 
   const std::string name_;
   Thread service_thread_;
@@ skipping 14 matching lines @@
   AtomicFlag join_for_testing_returned_;
 #endif
 
   DISALLOW_COPY_AND_ASSIGN(TaskSchedulerImpl);
 };
 
 }  // namespace internal
 }  // namespace base
 
 #endif  // BASE_TASK_SCHEDULER_TASK_SCHEDULER_IMPL_H_