mash: Remove shelf util functions; use WmWindow properties.

ash/shell/window_watcher.cc

Index: ash/shell/window_watcher.cc
diff --git a/ash/shell/window_watcher.cc b/ash/shell/window_watcher.cc
index a32999692a9c0cc9988e776334ce9772bb109493..e9b7fe04b82f467141a25a09c2471454ef42de9b 100644
--- a/ash/shell/window_watcher.cc
+++ b/ash/shell/window_watcher.cc
@@ -6,12 +6,13 @@
 
 #include <utility>
 
+#include "ash/aura/wm_window_aura.h"
 #include "ash/common/shelf/shelf_model.h"
 #include "ash/common/shelf/shelf_widget.h"
 #include "ash/common/shell_window_ids.h"
 #include "ash/common/wm_shell.h"
+#include "ash/common/wm_window_property.h"
 #include "ash/display/window_tree_host_manager.h"
-#include "ash/shelf/shelf_util.h"
 #include "ash/shell.h"
 #include "ash/shell/window_watcher_shelf_item_delegate.h"
 #include "ash/wm/window_util.h"
@@ -115,7 +116,7 @@ void WindowWatcher::OnWindowAdded(aura::Window* new_window) {
   std::unique_ptr<ShelfItemDelegate> delegate(
       new WindowWatcherShelfItemDelegate(id, this));
   model->SetShelfItemDelegate(id, std::move(delegate));
-  SetShelfIDForWindow(id, new_window);
+  WmWindowAura::Get(new_window)->SetIntProperty(WmWindowProperty::SHELF_ID, id);
 }
 
 void WindowWatcher::OnWillRemoveWindow(aura::Window* window) {