cros: Add close icon to task manager shelf context menu.

Bug: 889637
Change-Id: I75e48b670bc237761f0bc9a786dac1fcc1b2b529
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1617558Reviewed-by: Xiyuan Xia <xiyuan@chromium.org>
Commit-Queue: Matthew Mourgos <mmourgos@chromium.org>
Cr-Commit-Position: refs/heads/master@{#661077}

ash/shelf/shelf_window_watcher_item_delegate.cc

@@ -17,6 +17,9 @@
 #include "ui/aura/client/aura_constants.h"
 #include "ui/aura/window.h"
 #include "ui/events/event_constants.h"
+#include "ui/gfx/paint_vector_icon.h"
+#include "ui/views/controls/menu/menu_config.h"
+#include "ui/views/vector_icons.h"
 #include "ui/wm/core/window_animations.h"
 
 namespace ash {
@@ -62,7 +65,11 @@ void ShelfWindowWatcherItemDelegate::GetContextMenu(
     GetContextMenuCallback callback) {
   auto menu = std::make_unique<ShelfContextMenuModel>(this, display_id);
   // Show a default context menu with just an extra close item.
-  menu->AddItemWithStringId(kCloseCommandId, IDS_CLOSE);
+  const views::MenuConfig& menu_config = views::MenuConfig::instance();
+  menu->AddItemWithStringIdAndIcon(
+      kCloseCommandId, IDS_CLOSE,
+      gfx::CreateVectorIcon(views::kCloseIcon, menu_config.touchable_icon_size,
+                            menu_config.touchable_icon_color));
   std::move(callback).Run(std::move(menu));
 }