TaskScheduler: Add TaskTraits::WithWait().

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 d06a84dc1f47dd7a4cb16f4463a4fa0c486a6dca..03f161e0d1c25f1de5c76f897d0f0e1709801bd3 100644
--- a/base/task_scheduler/task_tracker.cc
+++ b/base/task_scheduler/task_tracker.cc
@@ -226,6 +226,9 @@ bool TaskTracker::RunTask(std::unique_ptr<Task> task,
         task->traits.shutdown_behavior() !=
         TaskShutdownBehavior::CONTINUE_ON_SHUTDOWN);
 
+    const bool previous_wait_allowed =
+        ThreadRestrictions::SetWaitAllowed(task->traits.with_wait());
+
     {
       // Set up SequenceToken as expected for the scope of the task.
       ScopedSetSequenceTokenForCurrentThread
@@ -261,6 +264,8 @@ bool TaskTracker::RunTask(std::unique_ptr<Task> task,
       PerformRunTask(std::move(task));
     }
 
+    ThreadRestrictions::SetWaitAllowed(previous_wait_allowed);
+
     AfterRunTask(shutdown_behavior);
   }