Migrate base::TaskRunner from Closure to OnceClosure

base/test/null_task_runner.h

Index: base/test/null_task_runner.h
diff --git a/base/test/null_task_runner.h b/base/test/null_task_runner.h
index a47e7b288c0666c1448e3edc029f24a567e6d814..3dd9d7e59738035bba4d325da60733d838ce1e59 100644
--- a/base/test/null_task_runner.h
+++ b/base/test/null_task_runner.h
@@ -20,10 +20,10 @@ class NullTaskRunner : public base::SingleThreadTaskRunner {
   NullTaskRunner();
 
   bool PostDelayedTask(const tracked_objects::Location& from_here,
-                       base::Closure task,
+                       base::OnceClosure task,
                        base::TimeDelta delay) override;
   bool PostNonNestableDelayedTask(const tracked_objects::Location& from_here,
-                                  base::Closure task,
+                                  base::OnceClosure task,
                                   base::TimeDelta delay) override;
   // Always returns true to avoid triggering DCHECKs.
   bool RunsTasksOnCurrentThread() const override;