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

ui/aura/mus/mus_mouse_location_updater.cc

Index: ui/aura/mus/mus_mouse_location_updater.cc
diff --git a/ui/aura/mus/mus_mouse_location_updater.cc b/ui/aura/mus/mus_mouse_location_updater.cc
index cbf89bd620a7980583599cc32916739fda36b711..fbb43f27f908b7826dfadc69f8b7b30d4c44298b 100644
--- a/ui/aura/mus/mus_mouse_location_updater.cc
+++ b/ui/aura/mus/mus_mouse_location_updater.cc
@@ -29,11 +29,11 @@ bool IsMouseEventWithLocation(const ui::Event& event) {
 }  // 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) {
@@ -60,7 +60,7 @@ void MusMouseLocationUpdater::UseCursorScreenPoint() {
   Env::GetInstance()->get_last_mouse_location_from_mus_ = true;
 }
 
-void MusMouseLocationUpdater::OnBeginNestedMessageLoop() {
+void MusMouseLocationUpdater::OnBeginNestedRunLoop() {
   UseCursorScreenPoint();
 }