Add a new Theme widget to control color and text color of apps

sky/sdk/lib/theme/theme_data.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.
 
-#include "malloc_wrapper.h"
+import 'dart:sky';
 
-#include <stdlib.h>
+import 'typography.dart';
 
-void* MallocWrapper(size_t size) {
-  return malloc(size);
+class ThemeData {
+  const ThemeData({ this.text, this.color });
+  final TextTheme text;
+  final Map<int, Color> color;
 }