Revert "Add a Color class to dart:sky."

sky/engine/core/painting/Color.dart

Index: sky/engine/core/painting/Color.dart
diff --git a/sky/engine/core/painting/Color.dart b/sky/engine/core/painting/Color.dart
deleted file mode 100644
index b88e3b45619e84bac46be5ead6773ac2e3a20fcc..0000000000000000000000000000000000000000
--- a/sky/engine/core/painting/Color.dart
+++ /dev/null
@@ -1,18 +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.
-
-part of dart.sky;
-
-class Color {
-  final int _value;
-  int get value => _value;
-
-  const Color(this._value);
-  const Color.fromARGB(int a, int r, int g, int b) :
-    _value = (((a & 0xff) << 24) |
-              ((r & 0xff) << 16) |
-              ((g & 0xff) << 8) |
-              ((b & 0xff) << 0));
-
-}