TaskScheduler: Add TaskTraits::WithWait().

base/task_scheduler/task_traits.cc

Index: base/task_scheduler/task_traits.cc
diff --git a/base/task_scheduler/task_traits.cc b/base/task_scheduler/task_traits.cc
index 10cbe68efcfc4c97d14be08848ad54ba7d68ce95..437189c05d44fa824ba471a8f42b0fabde647b23 100644
--- a/base/task_scheduler/task_traits.cc
+++ b/base/task_scheduler/task_traits.cc
@@ -17,6 +17,7 @@ namespace base {
 // request defaults if the behavior is critical to the task.
 TaskTraits::TaskTraits()
     : with_file_io_(false),
+      with_wait_(false),
       priority_(TaskPriority::BACKGROUND),
       shutdown_behavior_(TaskShutdownBehavior::SKIP_ON_SHUTDOWN) {}
 
@@ -27,6 +28,11 @@ TaskTraits& TaskTraits::WithFileIO() {
   return *this;
 }
 
+TaskTraits& TaskTraits::WithWait() {
+  with_wait_ = true;
+  return *this;
+}
+
 TaskTraits& TaskTraits::WithPriority(TaskPriority priority) {
   priority_ = priority;
   return *this;