TaskScheduler: Record TaskScheduler.NumTasksBeforeDetach.* from OnDetach().

base/task_scheduler/scheduler_worker_stack_unittest.cc

Index: base/task_scheduler/scheduler_worker_stack_unittest.cc
diff --git a/base/task_scheduler/scheduler_worker_stack_unittest.cc b/base/task_scheduler/scheduler_worker_stack_unittest.cc
index 022e1961de6f9c02d67ace0a911c2dce9ebc6e16..5359dcd0ebc4f225fc758342cb5eecbf688bad2b 100644
--- a/base/task_scheduler/scheduler_worker_stack_unittest.cc
+++ b/base/task_scheduler/scheduler_worker_stack_unittest.cc
@@ -22,8 +22,7 @@ namespace {
 
 class MockSchedulerWorkerDelegate : public SchedulerWorker::Delegate {
  public:
-  void OnMainEntry(SchedulerWorker* worker,
-                   const TimeDelta& detach_duration) override {}
+  void OnMainEntry(SchedulerWorker* worker) override {}
   scoped_refptr<Sequence> GetWork(SchedulerWorker* worker) override {
     return nullptr;
   }
@@ -40,6 +39,7 @@ class MockSchedulerWorkerDelegate : public SchedulerWorker::Delegate {
   bool CanDetach(SchedulerWorker* worker) override {
     return false;
   }
+  void OnDetach() override { ADD_FAILURE() << "Unexpected call to OnDetach()"; }
 };
 
 class TaskSchedulerWorkerStackTest : public testing::Test {