[scheduler]: Avoid waking up the scheduler to end long idle periods.

components/scheduler/child/nestable_task_runner_for_test.h

Index: components/scheduler/child/nestable_task_runner_for_test.h
diff --git a/components/scheduler/child/nestable_task_runner_for_test.h b/components/scheduler/child/nestable_task_runner_for_test.h
index 69056204872eca8e3199f0e25b2225f4a1c51491..6ebf3d396cbfb9bc165d78957d551537cb189deb 100644
--- a/components/scheduler/child/nestable_task_runner_for_test.h
+++ b/components/scheduler/child/nestable_task_runner_for_test.h
@@ -25,6 +25,9 @@ class NestableTaskRunnerForTest : public NestableSingleThreadTaskRunner {
                                   base::TimeDelta delay) override;
   bool RunsTasksOnCurrentThread() const override;
   bool IsNested() const override;
+  void AddTaskObserver(base::MessageLoop::TaskObserver* task_observer) override;
+  void RemoveTaskObserver(
+      base::MessageLoop::TaskObserver* task_observer) override;
 
  protected:
   ~NestableTaskRunnerForTest() override;
@@ -33,9 +36,16 @@ class NestableTaskRunnerForTest : public NestableSingleThreadTaskRunner {
   NestableTaskRunnerForTest(
       scoped_refptr<base::SingleThreadTaskRunner> task_runner);
 
+  void WrapTask(const base::PendingTask* wrapped_task);
+
   scoped_refptr<base::SingleThreadTaskRunner> task_runner_;
   bool is_nested_;
 
+  ObserverList<base::MessageLoop::TaskObserver> task_observers_;
+
+  base::WeakPtr<NestableTaskRunnerForTest> weak_nestable_task_runner_ptr_;
+  base::WeakPtrFactory<NestableTaskRunnerForTest> weak_factory_;
+
   DISALLOW_COPY_AND_ASSIGN(NestableTaskRunnerForTest);
 };