Forgot to update BUILD.gn when I renamed ui_node.dart.

sky/sdk/BUILD.gn

 # Copyright 2015 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 import("//mojo/public/dart/rules.gni")
 
 dart_pkg("sdk") {
   sources = [
     "CHANGELOG.md",
     "README.md",
@@ skipping 106 matching lines @@
     "lib/widgets/navigator.dart",
     "lib/widgets/popup_menu.dart",
     "lib/widgets/popup_menu_item.dart",
     "lib/widgets/radio.dart",
     "lib/widgets/raised_button.dart",
     "lib/widgets/scaffold.dart",
     "lib/widgets/scrollable.dart",
     "lib/widgets/switch.dart",
     "lib/widgets/toggleable.dart",
     "lib/widgets/tool_bar.dart",
-    "lib/widgets/ui_node.dart",
+    "lib/widgets/widget.dart",
     "pubspec.yaml",
   ]
 
   # List of mojom targets that the sky pkg exports
   deps = [
     "//sky/services/viewport",
   ]
 
   datadeps = [
     "//sky/services/testing:bindings",
     "//sky/engine/bindings",
   ]
 
   sdk_ext_directory = "$root_gen_dir/sky/bindings"
 }