Refactors DockedWindowLayoutManager in terms of ash/wm/common

ash/shell.cc

Index: ash/shell.cc
diff --git a/ash/shell.cc b/ash/shell.cc
index ed74ab40e0bd47bc75e32f9bf87000e03f568522..8a7284a78954a8b625f93061dbf10090a4b5a0c2 100644
--- a/ash/shell.cc
+++ b/ash/shell.cc
@@ -517,12 +517,13 @@ ShelfAutoHideBehavior Shell::GetShelfAutoHideBehavior(
   return Shelf::ForWindow(root_window)->auto_hide_behavior();
 }
 
-void Shell::SetShelfAlignment(ShelfAlignment alignment,
+void Shell::SetShelfAlignment(wm::ShelfAlignment alignment,
                               aura::Window* root_window) {
   Shelf::ForWindow(root_window)->SetAlignment(alignment);
 }
 
-ShelfAlignment Shell::GetShelfAlignment(const aura::Window* root_window) const {
+wm::ShelfAlignment Shell::GetShelfAlignment(
+    const aura::Window* root_window) const {
   return Shelf::ForWindow(root_window)->alignment();
 }