Redirect the MessageLoop's task runner to the renderer scheduler

components/scheduler/child/webthread_impl_for_worker_scheduler.cc

Index: components/scheduler/child/webthread_impl_for_worker_scheduler.cc
diff --git a/components/scheduler/child/webthread_impl_for_worker_scheduler.cc b/components/scheduler/child/webthread_impl_for_worker_scheduler.cc
index 87ac8208c746bd5b5b01dc10baa27ba93c296749..cf9322dfb882860989488722057e0a34c495f580 100644
--- a/components/scheduler/child/webthread_impl_for_worker_scheduler.cc
+++ b/components/scheduler/child/webthread_impl_for_worker_scheduler.cc
@@ -8,7 +8,7 @@
 #include "base/location.h"
 #include "base/single_thread_task_runner.h"
 #include "base/synchronization/waitable_event.h"
-#include "components/scheduler/child/scheduler_message_loop_delegate.h"
+#include "components/scheduler/child/scheduler_task_runner_delegate_impl.h"
 #include "components/scheduler/child/web_scheduler_impl.h"
 #include "components/scheduler/child/worker_scheduler_impl.h"
 #include "third_party/WebKit/public/platform/WebTraceLocation.h"
@@ -19,21 +19,31 @@ WebThreadImplForWorkerScheduler::WebThreadImplForWorkerScheduler(
     const char* name)
     : thread_(new base::Thread(name)) {
   thread_->Start();
+  thread_task_runner_ = thread_->task_runner();
 
   base::WaitableEvent completion(false, false);
-  thread_->task_runner()->PostTask(
+  thread_task_runner_->PostTask(
       FROM_HERE, base::Bind(&WebThreadImplForWorkerScheduler::InitOnThread,
                             base::Unretained(this), &completion));
   completion.Wait();
 }
 
 WebThreadImplForWorkerScheduler::~WebThreadImplForWorkerScheduler() {
+  base::WaitableEvent completion(false, false);
+  // Restore the original task runner so that the thread can tear itself down.
+  thread_task_runner_->PostTask(
+      FROM_HERE,
+      base::Bind(&WebThreadImplForWorkerScheduler::RestoreTaskRunnerOnThread,
+                 base::Unretained(this), &completion));
+  completion.Wait();
   thread_->Stop();
 }
 
 void WebThreadImplForWorkerScheduler::InitOnThread(
     base::WaitableEvent* completion) {
-  worker_scheduler_ = WorkerScheduler::Create(thread_->message_loop());
+  task_runner_delegate_ =
+      SchedulerTaskRunnerDelegateImpl::Create(thread_->message_loop());
+  worker_scheduler_ = WorkerScheduler::Create(task_runner_delegate_);
   worker_scheduler_->Init();
   task_runner_ = worker_scheduler_->DefaultTaskRunner();
   idle_task_runner_ = worker_scheduler_->IdleTaskRunner();
@@ -45,6 +55,12 @@ void WebThreadImplForWorkerScheduler::InitOnThread(
   completion->Signal();
 }
 
+void WebThreadImplForWorkerScheduler::RestoreTaskRunnerOnThread(
+    base::WaitableEvent* completion) {
+  task_runner_delegate_->RestoreDefaultTaskRunner();
+  completion->Signal();
+}
+
 void WebThreadImplForWorkerScheduler::WillDestroyCurrentMessageLoop() {
   task_runner_ = nullptr;
   idle_task_runner_ = nullptr;