Refactors DockedWindowLayoutManager in terms of ash/wm/common

ash/system/tray/tray_image_item.cc

Index: ash/system/tray/tray_image_item.cc
diff --git a/ash/system/tray/tray_image_item.cc b/ash/system/tray/tray_image_item.cc
index ba81d02b9a96017af51b267a3cf903028d15ff5c..fc5d750d65917c514931a5dee4b2ef00108e171d 100644
--- a/ash/system/tray/tray_image_item.cc
+++ b/ash/system/tray/tray_image_item.cc
@@ -57,7 +57,8 @@ views::View* TrayImageItem::CreateDetailedView(user::LoginStatus status) {
 void TrayImageItem::UpdateAfterLoginStatusChange(user::LoginStatus status) {
 }
 
-void TrayImageItem::UpdateAfterShelfAlignmentChange(ShelfAlignment alignment) {
+void TrayImageItem::UpdateAfterShelfAlignmentChange(
+    wm::ShelfAlignment alignment) {
   SetTrayImageItemBorder(tray_view_, alignment);
   SetItemAlignment(alignment);
 }
@@ -72,7 +73,7 @@ void TrayImageItem::DestroyDefaultView() {
 void TrayImageItem::DestroyDetailedView() {
 }
 
-void TrayImageItem::SetItemAlignment(ShelfAlignment alignment) {
+void TrayImageItem::SetItemAlignment(wm::ShelfAlignment alignment) {
   // Center the item dependent on the orientation of the shelf.
   views::BoxLayout::Orientation layout = IsHorizontalAlignment(alignment)
                                              ? views::BoxLayout::kHorizontal