Add black and white constants to theme's colors.

sky/sdk/lib/theme/colors.dart

 // 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 'dart:sky' show Color;
 
+/// [Color] constants which represent Material design's
+/// [color palette](http://www.google.com/design/spec/style/color.html).
+
+const White = const Color(0xFFFFFFFF);
+const Black = const Color(0x00000000);
+
 const Map<int, Color> Red = const {
    50: const Color(0xFFFFEBEE),
   100: const Color(0xFFFFCDD2),
   200: const Color(0xFFEF9A9A),
   300: const Color(0xFFE57373),
   400: const Color(0xFFEF5350),
   500: const Color(0xFFF44336),
   600: const Color(0xFFE53935),
   700: const Color(0xFFD32F2F),
   800: const Color(0xFFC62828),
@@ skipping 227 matching lines @@
   100: const Color(0xFFCFD8DC),
   200: const Color(0xFFB0BEC5),
   300: const Color(0xFF90A4AE),
   400: const Color(0xFF78909C),
   500: const Color(0xFF607D8B),
   600: const Color(0xFF546E7A),
   700: const Color(0xFF455A64),
   800: const Color(0xFF37474F),
   900: const Color(0xFF263238),
 };