mash: remove more shell/shelf WmWindow usage.

ash/shelf/wm_shelf.h

Index: ash/shelf/wm_shelf.h
diff --git a/ash/shelf/wm_shelf.h b/ash/shelf/wm_shelf.h
index 491f35e1b3ae4369371787afdf5671ffad546928..6da8885b281b2bfb505282479fe11f2ba8219aed 100644
--- a/ash/shelf/wm_shelf.h
+++ b/ash/shelf/wm_shelf.h
@@ -12,6 +12,10 @@
 #include "ash/shelf/shelf_layout_manager_observer.h"
 #include "base/observer_list.h"
 
+namespace aura {
+class Window;
+}
+
 namespace gfx {
 class Rect;
 }
@@ -42,7 +46,7 @@ class ASH_EXPORT WmShelf : public ShelfLayoutManagerObserver {
 
   // Returns the shelf for the display that |window| is on. Note that the shelf
   // widget may not exist, or the shelf may not be visible.
-  static WmShelf* ForWindow(WmWindow* window);
+  static WmShelf* ForWindow(aura::Window* window);
 
   // Returns if shelf alignment options are enabled, and the user is able to
   // adjust the alignment (eg. not allowed in guest and supervised user modes).