Refactors DockedWindowLayoutManager in terms of ash/wm/common

ash/shell.h

Index: ash/shell.h
diff --git a/ash/shell.h b/ash/shell.h
index ad61d18ff6446e19a824f65b601e4e06173dbe05..eb5d02c5723bdfb24979e553a3d321bf7c0c1c8a 100644
--- a/ash/shell.h
+++ b/ash/shell.h
@@ -466,8 +466,9 @@ class ASH_EXPORT Shell : public SystemModalContainerEventFilterDelegate,
       aura::Window* root_window) const;
 
   // Sets/gets shelf's alignment on |root_window|.
-  void SetShelfAlignment(ShelfAlignment alignment, aura::Window* root_window);
-  ShelfAlignment GetShelfAlignment(const aura::Window* root_window) const;
+  void SetShelfAlignment(wm::ShelfAlignment alignment,
+                         aura::Window* root_window);
+  wm::ShelfAlignment GetShelfAlignment(const aura::Window* root_window) const;
 
   // Called when the alignment for a shelf changes.
   void OnShelfAlignmentChanged(aura::Window* root_window);