Rationalize Dart mojo and sky package structure

sky/framework/theme/shadows.dart

Index: sky/framework/theme/shadows.dart
diff --git a/sky/framework/theme/shadows.dart b/sky/framework/theme/shadows.dart
deleted file mode 100644
index 6c0d8ee5f7b1d2d85f686d14daee73ab9d83d98d..0000000000000000000000000000000000000000
--- a/sky/framework/theme/shadows.dart
+++ /dev/null
@@ -1,11 +0,0 @@
-// 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.
-
-const Map<int, String> Shadow = const {
-  1: '0  1px  3px rgba(0,0,0,0.12), 0  1px  2px rgba(0,0,0,0.24)',
-  2: '0  3px  6px rgba(0,0,0,0.16), 0  3px  6px rgba(0,0,0,0.23)',
-  3: '0 10px 20px rgba(0,0,0,0.19), 0  6px  6px rgba(0,0,0,0.23)',
-  4: '0 14px 28px rgba(0,0,0,0.25), 0 10px 10px rgba(0,0,0,0.22)',
-  5: '0 19px 38px rgba(0,0,0,0.30), 0 15px 12px rgba(0,0,0,0.22)',
-};