TaskScheduler: No BACKGROUND threads when unsupported.

base/task_scheduler/scheduler_worker_pool_params.cc

Index: base/task_scheduler/scheduler_worker_pool_params.cc
diff --git a/base/task_scheduler/scheduler_worker_pool_params.cc b/base/task_scheduler/scheduler_worker_pool_params.cc
index 14ee5840a52555872b7ed35c6b7d6796fce72e6d..d820460e91dace499c3e7ad9162a44b67faaa3a8 100644
--- a/base/task_scheduler/scheduler_worker_pool_params.cc
+++ b/base/task_scheduler/scheduler_worker_pool_params.cc
@@ -10,12 +10,12 @@ namespace base {
 
 SchedulerWorkerPoolParams::SchedulerWorkerPoolParams(
     const std::string& name,
-    ThreadPriority thread_priority,
+    ThreadPriority priority_hint,
     IORestriction io_restriction,
     int max_threads,
     const TimeDelta& suggested_reclaim_time)
     : name_(name),
-      thread_priority_(thread_priority),
+      priority_hint_(priority_hint),
       io_restriction_(io_restriction),
       max_threads_(max_threads),
       suggested_reclaim_time_(suggested_reclaim_time) {}