Refactors DockedWindowLayoutManager in terms of ash/wm/common

ash/system/tray/system_tray.h

Index: ash/system/tray/system_tray.h
diff --git a/ash/system/tray/system_tray.h b/ash/system/tray/system_tray.h
index 757ad0cd7f9938e792ed2cddb97d0f7bb20c6cc8..c966388e80b255af75c2687f7f95a7657b243e15 100644
--- a/ash/system/tray/system_tray.h
+++ b/ash/system/tray/system_tray.h
@@ -84,7 +84,7 @@ class ASH_EXPORT SystemTray : public TrayBackgroundView,
   void UpdateAfterLoginStatusChange(user::LoginStatus login_status);
 
   // Updates the items when the shelf alignment changes.
-  void UpdateAfterShelfAlignmentChange(ShelfAlignment alignment);
+  void UpdateAfterShelfAlignmentChange(wm::ShelfAlignment alignment);
 
   // Temporarily hides/unhides the notification bubble.
   void SetHideNotifications(bool hidden);
@@ -124,7 +124,7 @@ class ASH_EXPORT SystemTray : public TrayBackgroundView,
   bool CloseNotificationBubbleForTest() const;
 
   // Overridden from TrayBackgroundView.
-  void SetShelfAlignment(ShelfAlignment alignment) override;
+  void SetShelfAlignment(wm::ShelfAlignment alignment) override;
   void AnchorUpdated() override;
   base::string16 GetAccessibleNameForTray() override;
   void BubbleResized(const views::TrayBubbleView* bubble_view) override;