Fix two minor issues with sky/sdk

1) BUILD.gn was missing internals.dart.
2) generators.dart was importing scheduler.dart from the wrong directory.

TBR=eseidel@chromium.org

Review URL: https://codereview.chromium.org/1189523003.

sdk/BUILD.gn

@@ -84,6 +84,7 @@ dart_pkg("sdk") {
     "lib/framework/theme/shadows.dart",
     "lib/framework/theme/typography.dart",
     "lib/framework/theme/view_configuration.dart",
+    "lib/internals.dart",
     "lib/painting/box_painter.dart",
     "lib/painting/shadows.dart",
     "lib/rendering/block.dart",

sdk/lib/framework/animation/generators.dart

@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-import '../app/scheduler.dart' as scheduler;
+import '../../app/scheduler.dart' as scheduler;
 import 'curves.dart';
 import 'dart:async';
 import 'dart:math' as math;