Revert of Add ScopedTaskEnvironment::ExecutionControlMode.

base/task_scheduler/task_tracker.cc

Index: base/task_scheduler/task_tracker.cc
diff --git a/base/task_scheduler/task_tracker.cc b/base/task_scheduler/task_tracker.cc
index 5509e3219cb563bc9063c76d4dea6b2b5af64d31..55230aa93742ee3c58da9d43a2a67dc72d452cd8 100644
--- a/base/task_scheduler/task_tracker.cc
+++ b/base/task_scheduler/task_tracker.cc
@@ -388,10 +388,6 @@
 }
 #endif
 
-int TaskTracker::GetNumPendingUndelayedTasksForTesting() const {
-  return subtle::Acquire_Load(&num_pending_undelayed_tasks_);
-}
-
 bool TaskTracker::BeforePostTask(TaskShutdownBehavior shutdown_behavior) {
   if (shutdown_behavior == TaskShutdownBehavior::BLOCK_SHUTDOWN) {
     // BLOCK_SHUTDOWN tasks block shutdown between the moment they are posted