Refactors DockedWindowLayoutManager in terms of ash/wm/common

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 2e12dc11061a502e36206ce6799994e7b8ebe696..5659f86520498aafbfbd3666334a52084385c391 100644
--- a/ash/system/web_notification/web_notification_tray.h
+++ b/ash/system/web_notification/web_notification_tray.h
@@ -77,7 +77,7 @@ class ASH_EXPORT WebNotificationTray
   void UpdateAfterLoginStatusChange(user::LoginStatus login_status);
 
   // Overridden from TrayBackgroundView.
-  void SetShelfAlignment(ShelfAlignment alignment) override;
+  void SetShelfAlignment(wm::ShelfAlignment alignment) override;
   void AnchorUpdated() override;
   base::string16 GetAccessibleNameForTray() override;
   void HideBubbleWithView(const views::TrayBubbleView* bubble_view) override;