Add TaskScheduler::Create and TaskScheduler::CreateAndStartWithDefaultParams.

base/task_scheduler/task_scheduler.h

Index: base/task_scheduler/task_scheduler.h
diff --git a/base/task_scheduler/task_scheduler.h b/base/task_scheduler/task_scheduler.h
index fa786c88efe7580a8193edb0ac0020fdb26e1c68..8dc77ccdecd03f6c2e38eb054e2e2c227a8c69f7 100644
--- a/base/task_scheduler/task_scheduler.h
+++ b/base/task_scheduler/task_scheduler.h
@@ -135,28 +135,35 @@ class BASE_EXPORT TaskScheduler {
   // after this call.
   virtual void JoinForTesting() = 0;
 
-  // CreateAndSetSimpleTaskScheduler(), CreateAndSetDefaultTaskScheduler(), and
-  // SetInstance() register a TaskScheduler to handle tasks posted through the
-  // post_task.h API for this process. The registered TaskScheduler will only be
-  // deleted when a new TaskScheduler is registered and is leaked on shutdown.
-  // The methods must not be called when TaskRunners created by the previous
-  // TaskScheduler are still alive. The methods are not thread-safe; proper
-  // synchronization is required to use the post_task.h API after registering a
-  // new TaskScheduler.
+// CreateAndStartWithDefaultParams(), Create(), and SetInstance() register a

[robliao, 2017/04/24 22:37:27]

Discuss when one would use Create vs CreateAndStartWithDefaultParams.

[fdoray, 2017/04/25 21:56:11]

Done.

+// TaskScheduler to handle tasks posted through the post_task.h API for this
+// process. The registered TaskScheduler will only be deleted when a new
+// TaskScheduler is registered and is leaked on shutdown. The methods must not
+// be called when TaskRunners created by the previous TaskScheduler are still
+// alive. The methods are not thread-safe; proper synchronization is required to
+// use the post_task.h API after registering a new TaskScheduler.
 
 #if !defined(OS_NACL)
-  // Creates and sets a task scheduler using default params. |name| is used to
+  // Creates and starts a task scheduler using default params. |name| is used to
   // label threads and histograms. It should identify the component that calls
-  // this. CHECKs on failure. For tests, prefer base::test::ScopedTaskScheduler
-  // (ensures isolation).
+  // this. Start() is called by this method; it is invalid to call it again
+  // afterwards. CHECKs on failure. For tests, prefer
+  // base::test::ScopedTaskEnvironment (ensures isolation).
+  static void CreateAndStartWithDefaultParams(StringPiece name);
+
+  // Deprecated.
   static void CreateAndSetSimpleTaskScheduler(StringPiece name);
 #endif  // !defined(OS_NACL)
 
-  // Creates and sets a task scheduler using custom params. |name| is used to
-  // label threads and histograms. It should identify the component that creates
-  // the TaskScheduler. |init_params| is used to initialize the worker pools.
-  // CHECKs on failure. For tests, prefer base::test::ScopedTaskScheduler
-  // (ensures isolation).
+  // Creates a task scheduler. |name| is used to label threads and histograms.

[robliao, 2017/04/24 22:37:27]

Creates a ready to start task scheduler.

[fdoray, 2017/04/25 21:56:10]

Done.

+  // It should identify the component that creates the TaskScheduler. The task
+  // scheduler doesn't create threads until Start() is called on
+  // TaskScheduler::GetInstance(). Tasks can be posted before Start() is called,
+  // but they don't run until Start() is called. For tests, prefer
+  // base::test::ScopedTaskEnvironment (ensures isolation).
+  static void Create(StringPiece name);
+
+  // Deprecated.
   static void CreateAndSetDefaultTaskScheduler(StringPiece name,
                                                const InitParams& init_params);