Separate the create and start phases in TaskSchedulerImpl.
The task scheduler doesn't create threads before Start() is called.
Tasks can be posted before Start(), but they don't run right away.
Tasks can only run once Start() has been called.
BUG=690706
Review-Url: https://codereview.chromium.org/2834063002
Cr-Commit-Position: refs/heads/master@{#467117}
diff --git a/base/task_scheduler/task_scheduler.h b/base/task_scheduler/task_scheduler.h
index 9c7207ef..3d3d5eb0 100644
--- a/base/task_scheduler/task_scheduler.h
+++ b/base/task_scheduler/task_scheduler.h
@@ -33,9 +33,16 @@
class HistogramBase;
// Interface for a task scheduler and static methods to manage the instance used
-// by the post_task.h API. Note: all base/task_scheduler users should go through
-// post_task.h instead of TaskScheduler except for the one callsite per process
-// which manages the process' instance.
+// by the post_task.h API.
+//
+// The task scheduler doesn't create threads until Start() is called. Tasks can
+// be posted at any time but will not run until after Start() is called.
+//
+// The instance methods of this class are thread-safe.
+//
+// Note: All base/task_scheduler users should go through post_task.h instead of
+// TaskScheduler except for the one callsite per process which manages the
+// process's instance.
class BASE_EXPORT TaskScheduler {
public:
struct BASE_EXPORT InitParams {
@@ -59,6 +66,10 @@
// returned.
virtual ~TaskScheduler() = default;
+ // Allows the task scheduler to create threads and run tasks following the
+ // |init_params| specification. CHECKs on failure.
+ virtual void Start(const InitParams& init_params) = 0;
+
// Posts |task| with a |delay| and specific |traits|. |delay| can be zero.
// For one off tasks that don't require a TaskRunner.
virtual void PostDelayedTaskWithTraits(
