mash: Move AutoHideEventHandler to WmShelfAura.

ash/mus/bridge/wm_shelf_mus.cc

Index: ash/mus/bridge/wm_shelf_mus.cc
diff --git a/ash/mus/bridge/wm_shelf_mus.cc b/ash/mus/bridge/wm_shelf_mus.cc
index 39e10de2d0cb8b2ec44291c154db4dc9a728b596..7971b0f559f543a891eb28ddd35d5b6731eeb8cb 100644
--- a/ash/mus/bridge/wm_shelf_mus.cc
+++ b/ash/mus/bridge/wm_shelf_mus.cc
@@ -116,14 +116,6 @@ bool WmShelfMus::ProcessGestureEvent(const ui::GestureEvent& event) {
   return false;
 }
 
-void WmShelfMus::UpdateAutoHideForMouseEvent(ui::MouseEvent* event) {
-  NOTIMPLEMENTED();
-}
-
-void WmShelfMus::UpdateAutoHideForGestureEvent(ui::GestureEvent* event) {
-  NOTIMPLEMENTED();
-}
-
 void WmShelfMus::AddObserver(WmShelfObserver* observer) {
   observers_.AddObserver(observer);
 }