Use OnceCallback on Mojo interfaces in //ash

ash/shelf/shelf_window_watcher_item_delegate.cc

Index: ash/shelf/shelf_window_watcher_item_delegate.cc
diff --git a/ash/shelf/shelf_window_watcher_item_delegate.cc b/ash/shelf/shelf_window_watcher_item_delegate.cc
index 43398d85350bf4e86c152ca78679c449b19cb878..001b25f187721c4be75e33e27fd677f56c67fa09 100644
--- a/ash/shelf/shelf_window_watcher_item_delegate.cc
+++ b/ash/shelf/shelf_window_watcher_item_delegate.cc
@@ -4,6 +4,8 @@
 
 #include "ash/shelf/shelf_window_watcher_item_delegate.h"
 
+#include <utility>
+
 #include "ash/public/cpp/window_properties.h"
 #include "ash/shelf/shelf_controller.h"
 #include "ash/shelf/shelf_model.h"
@@ -40,28 +42,28 @@ void ShelfWindowWatcherItemDelegate::ItemSelected(
     std::unique_ptr<ui::Event> event,
     int64_t display_id,
     ShelfLaunchSource source,
-    const ItemSelectedCallback& callback) {
+    ItemSelectedCallback callback) {
   // Move panels attached on another display to the current display.
   if (GetShelfItemType(shelf_id()) == TYPE_APP_PANEL &&
       window_->aura_window()->GetProperty(kPanelAttachedKey) &&
       wm::MoveWindowToDisplay(window_->aura_window(), display_id)) {
     window_->Activate();
-    callback.Run(SHELF_ACTION_WINDOW_ACTIVATED, base::nullopt);
+    std::move(callback).Run(SHELF_ACTION_WINDOW_ACTIVATED, base::nullopt);
     return;
   }
 
   if (window_->IsActive()) {
     if (event && event->type() == ui::ET_KEY_RELEASED) {
       window_->Animate(::wm::WINDOW_ANIMATION_TYPE_BOUNCE);
-      callback.Run(SHELF_ACTION_NONE, base::nullopt);
+      std::move(callback).Run(SHELF_ACTION_NONE, base::nullopt);
       return;
     }
     window_->Minimize();
-    callback.Run(SHELF_ACTION_WINDOW_MINIMIZED, base::nullopt);
+    std::move(callback).Run(SHELF_ACTION_WINDOW_MINIMIZED, base::nullopt);
     return;
   }
   window_->Activate();
-  callback.Run(SHELF_ACTION_WINDOW_ACTIVATED, base::nullopt);
+  std::move(callback).Run(SHELF_ACTION_WINDOW_ACTIVATED, base::nullopt);
 }
 
 void ShelfWindowWatcherItemDelegate::ExecuteCommand(uint32_t command_id,