Make nesting/running states a RunLoop rather than a MessageLoop concept.

ui/aura/mus/mus_mouse_location_updater.cc

 // Copyright 2017 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "ui/aura/mus/mus_mouse_location_updater.h"
 
 #include "ui/aura/env.h"
 #include "ui/events/event.h"
 
 namespace aura {
@@ skipping 11 matching lines @@
       return true;
     default:
       break;
   }
   return false;
 }
 
 }  // namespace
 
 MusMouseLocationUpdater::MusMouseLocationUpdater() {
-  base::MessageLoop::current()->AddNestingObserver(this);
+  base::RunLoop::AddNestingObserverOnCurrentThread(this);
 }
 
 MusMouseLocationUpdater::~MusMouseLocationUpdater() {
-  base::MessageLoop::current()->RemoveNestingObserver(this);
+  base::RunLoop::RemoveNestingObserverOnCurrentThread(this);
 }
 
 void MusMouseLocationUpdater::OnEventProcessingStarted(const ui::Event& event) {
   if (!IsMouseEventWithLocation(event) ||
       Env::GetInstance()->always_use_last_mouse_location_) {
     return;
   }
 
   is_processing_trigger_event_ = true;
   Env::GetInstance()->set_last_mouse_location(
       event.AsMouseEvent()->root_location());
   Env::GetInstance()->get_last_mouse_location_from_mus_ = false;
 }
 
 void MusMouseLocationUpdater::OnEventProcessingFinished() {
   UseCursorScreenPoint();
 }
 
 void MusMouseLocationUpdater::UseCursorScreenPoint() {
   if (!is_processing_trigger_event_)
     return;
 
   is_processing_trigger_event_ = false;
   Env::GetInstance()->get_last_mouse_location_from_mus_ = true;
 }
 
-void MusMouseLocationUpdater::OnBeginNestedMessageLoop() {
+void MusMouseLocationUpdater::OnBeginNestedRunLoop() {
   UseCursorScreenPoint();
 }
 
 }  // namespace aura