mash: Remove WmWindow usage from ash/system/web_notification

ash/system/web_notification/web_notification_tray.h

Index: ash/system/web_notification/web_notification_tray.h
diff --git a/ash/system/web_notification/web_notification_tray.h b/ash/system/web_notification/web_notification_tray.h
index 96bb9ed8412f0e87b2e22d12292cbbf109ea5580..fbba6d45c27ba8f4eabdea50579bf6526983391d 100644
--- a/ash/system/web_notification/web_notification_tray.h
+++ b/ash/system/web_notification/web_notification_tray.h
@@ -19,13 +19,9 @@
 #include "ui/message_center/message_center_tray_delegate.h"
 #include "ui/views/bubble/tray_bubble_view.h"
 
-// Status area tray for showing browser and app notifications. This hosts
-// a MessageCenter class which manages the notification list. This class
-// contains the Ash specific tray implementation.
-//
-// Note: These are not related to system notifications (i.e NotificationView
-// generated by SystemTrayItem). Visibility of one notification type or other
-// is controlled by StatusAreaWidget.
+namespace aura {
+class Window;
+}
 
 namespace message_center {
 class MessageCenter;
@@ -39,8 +35,14 @@ class SystemTray;
 class WebNotificationBubbleWrapper;
 class WebNotificationImage;
 class WebNotificationLabel;
-class WmWindow;
 
+// Status area tray for showing browser and app notifications. This hosts
+// a MessageCenter class which manages the notification list. This class
+// contains the Ash specific tray implementation.
+//
+// Note: These are not related to system notifications (i.e NotificationView
+// generated by SystemTrayItem). Visibility of one notification type or other
+// is controlled by StatusAreaWidget.
 class ASH_EXPORT WebNotificationTray
     : public TrayBackgroundView,
       public views::TrayBubbleView::Delegate,
@@ -49,7 +51,7 @@ class ASH_EXPORT WebNotificationTray
       public ui::SimpleMenuModel::Delegate {
  public:
   WebNotificationTray(WmShelf* shelf,
-                      WmWindow* status_area_window,
+                      aura::Window* status_area_window,
                       SystemTray* system_tray);
   ~WebNotificationTray() override;
 
@@ -153,7 +155,7 @@ class ASH_EXPORT WebNotificationTray
   bool IsPopupVisible() const;
   message_center::MessageCenterBubble* GetMessageCenterBubbleForTest();
 
-  WmWindow* status_area_window_;
+  aura::Window* status_area_window_;
   SystemTray* system_tray_;
   std::unique_ptr<message_center::MessageCenterTray> message_center_tray_;
   std::unique_ptr<WebNotificationBubbleWrapper> message_center_bubble_;