Add base::TaskTraits::Override().

base/task_scheduler/task.cc

Index: base/task_scheduler/task.cc
diff --git a/base/task_scheduler/task.cc b/base/task_scheduler/task.cc
index fc513e3e9fb53945bc22b21185430457e9e382ea..d97c78b0ffd3f4d6da9883f9d6803fdb59b7ba65 100644
--- a/base/task_scheduler/task.cc
+++ b/base/task_scheduler/task.cc
@@ -24,11 +24,12 @@ Task::Task(const tracked_objects::Location& posted_from,
           false),  // Not nestable.
       // Prevent a delayed BLOCK_SHUTDOWN task from blocking shutdown before
       // being scheduled by changing its shutdown behavior to SKIP_ON_SHUTDOWN.
-      traits(!delay.is_zero() && traits.shutdown_behavior() ==
-                                     TaskShutdownBehavior::BLOCK_SHUTDOWN
-                 ? TaskTraits(traits).WithShutdownBehavior(
-                       TaskShutdownBehavior::SKIP_ON_SHUTDOWN)
-                 : traits),
+      traits(TaskTraits::Merge(
+          traits,
+          {delay.is_zero() && traits.shutdown_behavior() ==
+                                  TaskShutdownBehavior::BLOCK_SHUTDOWN
+               ? TaskShutdownBehavior::SKIP_ON_SHUTDOWN
+               : traits.shutdown_behavior()})),

[gab, 2017/05/09 14:32:31]

This is weird, I'd prefer not doing anything by default and overriding if
BLOCK_SHUTDOWN && delay

[fdoray, 2017/05/09 14:58:33]

Done.

       delay(delay) {}
 
 Task::~Task() = default;