Move Task Scheduler Single Thread Task Runners to Dedicated Threads

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 0747c2ed2cd5bf8a3e92064fc97a74c0793f4be5..35ba8c245d305908e6c4158ac4d749bdb1789eed 100644
--- a/base/task_scheduler/scheduler_worker_pool_params.cc
+++ b/base/task_scheduler/scheduler_worker_pool_params.cc
@@ -21,6 +21,12 @@ SchedulerWorkerPoolParams::SchedulerWorkerPoolParams(
       backward_compatibility_(backward_compatibility) {}
 
 SchedulerWorkerPoolParams::SchedulerWorkerPoolParams(
+    const SchedulerWorkerPoolParams& other) = default;
+
+SchedulerWorkerPoolParams& SchedulerWorkerPoolParams::operator=(
+    const SchedulerWorkerPoolParams& other) = default;
+
+SchedulerWorkerPoolParams::SchedulerWorkerPoolParams(
     SchedulerWorkerPoolParams&& other) = default;
 
 SchedulerWorkerPoolParams& SchedulerWorkerPoolParams::operator=(