Add TaskScheduler.NumTasksBeforeDetach.[worker pool name] histogram.

base/task_scheduler/scheduler_worker_pool_impl.h

Index: base/task_scheduler/scheduler_worker_pool_impl.h
diff --git a/base/task_scheduler/scheduler_worker_pool_impl.h b/base/task_scheduler/scheduler_worker_pool_impl.h
index b5aa894e38afdaafce3c2933d46d4bf97ab7a6e3..cab7b87810299f5b79c0700103b9cfd857b537ff 100644
--- a/base/task_scheduler/scheduler_worker_pool_impl.h
+++ b/base/task_scheduler/scheduler_worker_pool_impl.h
@@ -94,7 +94,11 @@ class BASE_EXPORT SchedulerWorkerPoolImpl : public SchedulerWorkerPool {
                                scoped_refptr<Sequence> sequence,
                                SchedulerWorker* worker) override;
 
-  const HistogramBase* num_tasks_between_waits_histogram_for_testing() const {
+  const HistogramBase* num_tasks_before_detach_histogram() const {
+    return num_tasks_before_detach_histogram_;
+  }
+
+  const HistogramBase* num_tasks_between_waits_histogram() const {
     return num_tasks_between_waits_histogram_;
   }
 
@@ -188,6 +192,10 @@ class BASE_EXPORT SchedulerWorkerPoolImpl : public SchedulerWorkerPool {
   // leaked.
   HistogramBase* const detach_duration_histogram_;
 
+  // TaskScheduler.NumTasksBeforeDetach.[worker pool name] histogram.
+  // Intentionally leaked.
+  HistogramBase* const num_tasks_before_detach_histogram_;
+
   // TaskScheduler.NumTasksBetweenWaits.[worker pool name] histogram.
   // Intentionally leaked.
   HistogramBase* const num_tasks_between_waits_histogram_;