TaskScheduler: Add TaskRunnerHandle support to TaskScheduler tasks

base/task_scheduler/scheduler_thread_pool.cc

Index: base/task_scheduler/scheduler_thread_pool.cc
diff --git a/base/task_scheduler/scheduler_thread_pool.cc b/base/task_scheduler/scheduler_thread_pool.cc
index 203877d6dc4fe938d23c41cea86d4860cae2f036..ea231bf6446cb60e75d9c2f8b06609d93c0e6265 100644
--- a/base/task_scheduler/scheduler_thread_pool.cc
+++ b/base/task_scheduler/scheduler_thread_pool.cc
@@ -86,12 +86,14 @@ class SchedulerSequencedTaskRunner : public SequencedTaskRunner {
   bool PostDelayedTask(const tracked_objects::Location& from_here,
                        const Closure& closure,
                        TimeDelta delay) override {
+    std::unique_ptr<Task> task(
+        new Task(from_here, closure, traits_,
+                 delay.is_zero() ? TimeTicks() : TimeTicks::Now() + delay));
+    task->sequenced_task_runner_ref = this;
+
     // Post the task as part of |sequence|.
-    return PostTaskToExecutor(
-        WrapUnique(
-            new Task(from_here, closure, traits_,
-                     delay.is_zero() ? TimeTicks() : TimeTicks::Now() + delay)),
-        sequence_, executor_, task_tracker_, delayed_task_manager_);
+    return PostTaskToExecutor(std::move(task), sequence_, executor_,
+                              task_tracker_, delayed_task_manager_);
   }
 
   bool PostNonNestableDelayedTask(const tracked_objects::Location& from_here,