Revert of Redirect the MessageLoop's task runner to the renderer scheduler

components/scheduler/test/lazy_scheduler_message_loop_delegate_for_tests.cc

Index: components/scheduler/test/lazy_scheduler_message_loop_delegate_for_tests.cc
diff --git a/components/scheduler/test/lazy_scheduler_message_loop_delegate_for_tests.cc b/components/scheduler/test/lazy_scheduler_message_loop_delegate_for_tests.cc
index 9d613d65965a0b43555abce8a7a55cfc25c2098b..999d8567a1f03be79f526b42b6aa6340254a80df 100644
--- a/components/scheduler/test/lazy_scheduler_message_loop_delegate_for_tests.cc
+++ b/components/scheduler/test/lazy_scheduler_message_loop_delegate_for_tests.cc
@@ -16,13 +16,10 @@
     LazySchedulerMessageLoopDelegateForTests()
     : message_loop_(base::MessageLoop::current()),
       thread_id_(base::PlatformThread::CurrentId()) {
-  if (message_loop_)
-    original_task_runner_ = message_loop_->task_runner();
 }
 
 LazySchedulerMessageLoopDelegateForTests::
     ~LazySchedulerMessageLoopDelegateForTests() {
-  RestoreDefaultTaskRunner();
 }
 
 base::MessageLoop* LazySchedulerMessageLoopDelegateForTests::EnsureMessageLoop()
@@ -32,28 +29,11 @@
   DCHECK(RunsTasksOnCurrentThread());
   message_loop_ = base::MessageLoop::current();
   DCHECK(message_loop_);
-  original_task_runner_ = message_loop_->task_runner();
   for (auto& observer : pending_observers_) {
     message_loop_->AddTaskObserver(observer);
   }
   pending_observers_.clear();
-  if (pending_task_runner_)
-    message_loop_->SetTaskRunner(pending_task_runner_.Pass());
   return message_loop_;
-}
-
-void LazySchedulerMessageLoopDelegateForTests::SetDefaultTaskRunner(
-    scoped_refptr<base::SingleThreadTaskRunner> task_runner) {
-  if (!HasMessageLoop()) {
-    pending_task_runner_ = task_runner.Pass();
-    return;
-  }
-  message_loop_->SetTaskRunner(task_runner.Pass());
-}
-
-void LazySchedulerMessageLoopDelegateForTests::RestoreDefaultTaskRunner() {
-  if (HasMessageLoop() && base::MessageLoop::current() == message_loop_)
-    message_loop_->SetTaskRunner(original_task_runner_);
 }
 
 bool LazySchedulerMessageLoopDelegateForTests::HasMessageLoop() const {
@@ -64,17 +44,16 @@
     const tracked_objects::Location& from_here,
     const base::Closure& task,
     base::TimeDelta delay) {
-  EnsureMessageLoop();
-  return original_task_runner_->PostDelayedTask(from_here, task, delay);
+  return EnsureMessageLoop()->task_runner()->PostDelayedTask(from_here, task,
+                                                             delay);
 }
 
 bool LazySchedulerMessageLoopDelegateForTests::PostNonNestableDelayedTask(
     const tracked_objects::Location& from_here,
     const base::Closure& task,
     base::TimeDelta delay) {
-  EnsureMessageLoop();
-  return original_task_runner_->PostNonNestableDelayedTask(from_here, task,
-                                                           delay);
+  return EnsureMessageLoop()->task_runner()->PostNonNestableDelayedTask(
+      from_here, task, delay);
 }
 
 bool LazySchedulerMessageLoopDelegateForTests::RunsTasksOnCurrentThread()