Splits ToplevelWindowEventHandler into two

ash/wm/aura/wm_globals_aura.cc

Index: ash/wm/aura/wm_globals_aura.cc
diff --git a/ash/wm/aura/wm_globals_aura.cc b/ash/wm/aura/wm_globals_aura.cc
index 8600c83aee3524ef656486b2540a89ce09428f6d..17f107bd1910d5043d65b615e115cd6ac4dea6f7 100644
--- a/ash/wm/aura/wm_globals_aura.cc
+++ b/ash/wm/aura/wm_globals_aura.cc
@@ -166,6 +166,11 @@ void WmGlobalsAura::OnWindowActivated(
                                       WmWindowAura::Get(lost_active)));
 }
 
+void WmGlobalsAura::OnDisplayConfigurationChanging() {
+  FOR_EACH_OBSERVER(WmDisplayObserver, display_observers_,
+                    OnDisplayConfigurationChanging());
+}
+
 void WmGlobalsAura::OnDisplayConfigurationChanged() {
   FOR_EACH_OBSERVER(WmDisplayObserver, display_observers_,
                     OnDisplayConfigurationChanged());