TaskScheduler: Add TaskRunnerHandle support to TaskScheduler tasks

base/task_scheduler/scheduler_worker_thread.cc

Index: base/task_scheduler/scheduler_worker_thread.cc
diff --git a/base/task_scheduler/scheduler_worker_thread.cc b/base/task_scheduler/scheduler_worker_thread.cc
index 04117f213eda428e557cfd733693c38df0f65dc5..e0ed56eda133ef1dcf801f362e97a81fb05a9d72 100644
--- a/base/task_scheduler/scheduler_worker_thread.cc
+++ b/base/task_scheduler/scheduler_worker_thread.cc
@@ -44,12 +44,14 @@ class SchedulerSingleThreadTaskRunner : public SingleThreadTaskRunner {
   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->single_thread_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,