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

ash/app_list/app_list_presenter_delegate.cc

Index: ash/app_list/app_list_presenter_delegate.cc
diff --git a/ash/app_list/app_list_presenter_delegate.cc b/ash/app_list/app_list_presenter_delegate.cc
index d128d468ad34c49ca641791da44f7fbddeb2b662..4fdff264fc8452b754727542fefe8b17fed9237f 100644
--- a/ash/app_list/app_list_presenter_delegate.cc
+++ b/ash/app_list/app_list_presenter_delegate.cc
@@ -313,8 +313,7 @@ void AppListPresenterDelegate::OnKeyboardBoundsChanging(
 
 ////////////////////////////////////////////////////////////////////////////////
 // AppListPresenterDelegate, ShellObserver implementation:
-void AppListPresenterDelegate::OnShelfAlignmentChanged(
-    aura::Window* root_window) {
+void AppListPresenterDelegate::OnShelfAlignmentChanged(WmWindow* root_window) {
   if (view_)
     view_->SetBubbleArrow(GetBubbleArrow(view_->GetWidget()->GetNativeView()));
 }