Redirect the MessageLoop's task runner to the renderer scheduler

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 120fe0070e6de32f44c25b5d9912d8a60ded052d..674c74394ece7a01f899db08c697dd9bae990e11 100644
--- a/components/scheduler/child/nestable_task_runner_for_test.h
+++ b/components/scheduler/child/nestable_task_runner_for_test.h
@@ -17,6 +17,8 @@ class NestableTaskRunnerForTest : public NestableSingleThreadTaskRunner {
   void SetNested(bool is_nested);
 
   // NestableSingleThreadTaskRunner implementation
+  void SetDefaultTaskRunner(
+      scoped_refptr<base::SingleThreadTaskRunner> task_runner) override;
   bool PostDelayedTask(const tracked_objects::Location& from_here,
                        const base::Closure& task,
                        base::TimeDelta delay) override;
@@ -29,6 +31,10 @@ class NestableTaskRunnerForTest : public NestableSingleThreadTaskRunner {
   void RemoveTaskObserver(
       base::MessageLoop::TaskObserver* task_observer) override;
 
+  base::SingleThreadTaskRunner* default_task_runner() const {
+    return default_task_runner_.get();
+  }
+
  protected:
   ~NestableTaskRunnerForTest() override;
 
@@ -39,6 +45,7 @@ class NestableTaskRunnerForTest : public NestableSingleThreadTaskRunner {
   void WrapTask(const base::PendingTask* wrapped_task);
 
   scoped_refptr<base::SingleThreadTaskRunner> task_runner_;
+  scoped_refptr<base::SingleThreadTaskRunner> default_task_runner_;
   bool is_nested_;
 
   base::ObserverList<base::MessageLoop::TaskObserver> task_observers_;