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

ui/aura/mus/mus_mouse_location_updater.h

 // 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.
 
 #ifndef UI_AURA_MUS_MUS_MOUSE_LOCATION_UPDATER_H_
 #define UI_AURA_MUS_MUS_MOUSE_LOCATION_UPDATER_H_
 
 #include "base/macros.h"
-#include "base/message_loop/message_loop.h"
+#include "base/run_loop.h"
 
 namespace ui {
 class Event;
 }
 
 namespace aura {
 
 // MusMouseLocationUpdater is responsible for updating
 // Env::last_mouse_location(), as well as determining when
 // Env::last_mouse_location() should use
 // WindowTreeClient::GetCursorScreenPoint(). While processing an event
 // Env uses the value from the current event, otherwise Env uses
 // WindowTreeClient::GetCursorScreenPoint(). If a nested message loop is
 // started while processing an event Env uses GetCursorScreenPoint().
-class MusMouseLocationUpdater : public base::MessageLoop::NestingObserver {
+class MusMouseLocationUpdater : public base::RunLoop::NestingObserver {
  public:
   MusMouseLocationUpdater();
   ~MusMouseLocationUpdater() override;
 
   // Called from WindowEventDispatcher on starting/stopping processing of
   // events.
   void OnEventProcessingStarted(const ui::Event& event);
   void OnEventProcessingFinished();
 
  private:
   // Called to switch from using last event location to current cursor screen
   // location.
   void UseCursorScreenPoint();
 
-  // base::MessageLoop::NestingObserver:
-  void OnBeginNestedMessageLoop() override;
+  // base::RunLoop::NestingObserver:
+  void OnBeginNestedRunLoop() override;
 
   // Set to true while processing a valid mouse event.
   bool is_processing_trigger_event_ = false;
 
   DISALLOW_COPY_AND_ASSIGN(MusMouseLocationUpdater);
 };
 
 }  // namespace aura
 
 #endif  // UI_AURA_MUS_MUS_MOUSE_LOCATION_UPDATER_H_