Converts ShellObserver from aura::Window to ash::WmWindow

ash/shelf/shelf_window_watcher.h

Index: ash/shelf/shelf_window_watcher.h
diff --git a/ash/shelf/shelf_window_watcher.h b/ash/shelf/shelf_window_watcher.h
index c1d0a7cdf4008d3ff96c8f4478e35d3489b6117a..53cbdbf0be0ce6320f8804aeea468df6a617ed2d 100644
--- a/ash/shelf/shelf_window_watcher.h
+++ b/ash/shelf/shelf_window_watcher.h
@@ -29,6 +29,7 @@ namespace ash {
 
 class ShelfModel;
 class ShelfItemDelegateManager;
+class WmWindow;
 
 // ShelfWindowWatcher creates and handles a ShelfItem for windows that have
 // a ShelfItemDetails property in the default container.
@@ -81,8 +82,9 @@ class ShelfWindowWatcher : public aura::client::ActivationChangeObserver,
   // Removes a ShelfItem for |window|.
   void RemoveShelfItem(aura::Window* window);
 
-  // Adds observer to default container and ActivationClient of |root_window|.
-  void OnRootWindowAdded(aura::Window* root_window);
+  // Adds observer to default container and ActivationClient of
+  // |root_window_wm|.
+  void OnRootWindowAdded(WmWindow* root_window_wm);
 
   // Removes observer from ActivationClient of |root_window|.
   void OnRootWindowRemoved(aura::Window* root_window);