Material light and dark themes for Sky widgets

sky/sdk/lib/widgets/default_text_style.dart

Index: sky/sdk/lib/widgets/default_text_style.dart
diff --git a/sky/sdk/lib/widgets/default_text_style.dart b/sky/sdk/lib/widgets/default_text_style.dart
new file mode 100644
index 0000000000000000000000000000000000000000..a8cc5f0d14a2b43657bba8b01719493b0d3cebf0
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+++ b/sky/sdk/lib/widgets/default_text_style.dart
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+// 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 '../painting/text_style.dart';
+import 'basic.dart';
+import 'widget.dart';
+
+class DefaultTextStyle extends Inherited {
+
+  DefaultTextStyle({
+    String key,
+    this.style,
+    Widget child
+  }) : super(key: key, child: child) {
+    assert(style != null);
+    assert(child != null);
+  }
+
+  final TextStyle style;
+
+  static TextStyle of(Component component) {
+    DefaultTextStyle result = component.inheritedOfType(DefaultTextStyle);
+    return result == null ? null : result.style;
+  }
+}