Move function to compute the max number of threads in a TaskScheduler pool to base/.

base/BUILD.gn

Index: base/BUILD.gn
diff --git a/base/BUILD.gn b/base/BUILD.gn
index f92612de78e6ebb60dacf0986f652663ab2f7554..141dc2b7552a4bbbafa9824c1af0823ddd8a7910 100644
--- a/base/BUILD.gn
+++ b/base/BUILD.gn
@@ -792,6 +792,8 @@ component("base") {
     "task_runner_util.h",
     "task_scheduler/delayed_task_manager.cc",
     "task_scheduler/delayed_task_manager.h",
+    "task_scheduler/initialization_util.cc",
+    "task_scheduler/initialization_util.h",
     "task_scheduler/post_task.cc",
     "task_scheduler/post_task.h",
     "task_scheduler/priority_queue.cc",
@@ -1165,6 +1167,8 @@ component("base") {
       "synchronization/read_write_lock_posix.cc",
       "sys_info.cc",
       "sys_info_posix.cc",
+      "task_scheduler/initialization_util.cc",
+      "task_scheduler/initialization_util.h",
       "trace_event/trace_event_system_stats_monitor.cc",
     ]