Converts ShellObserver from aura::Window to ash::WmWindow

ash/shelf/shelf_layout_manager.cc

Index: ash/shelf/shelf_layout_manager.cc
diff --git a/ash/shelf/shelf_layout_manager.cc b/ash/shelf/shelf_layout_manager.cc
index a7916e6b6a922d77dcaa3df3af73f2681d112921..c09ab66d37e1d2bc0628be3f4f4d0e0c1ba011a4 100644
--- a/ash/shelf/shelf_layout_manager.cc
+++ b/ash/shelf/shelf_layout_manager.cc
@@ -551,13 +551,12 @@ void ShelfLayoutManager::OnLockStateChanged(bool locked) {
   UpdateShelfVisibilityAfterLoginUIChange();
 }
 
-void ShelfLayoutManager::OnShelfAlignmentChanged(aura::Window* root_window) {
+void ShelfLayoutManager::OnShelfAlignmentChanged(WmWindow* root_window) {
   if (Shell::GetInstance()->in_mus())
     LayoutShelf();
 }
 
-void ShelfLayoutManager::OnShelfAutoHideBehaviorChanged(
-    aura::Window* root_window) {
+void ShelfLayoutManager::OnShelfAutoHideBehaviorChanged(WmWindow* root_window) {
   UpdateVisibilityState();
 }