Support for icon theming

sky/sdk/lib/widgets/icon_theme.dart

+// Copyright 2015 The Chromium Authors. All rights reserved.

[Hixie, 2015/07/09 23:06:08]

Put this in icon.dart, since only icons, and people who care about icons, care
about this.

[jackson, 2015/07/09 23:16:19]

Done.

+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+import 'basic.dart';
+import 'widget.dart';
+
+enum IconThemeColor { white, black }
+
+class IconThemeData {
+  const IconThemeData({ this.color });
+  final IconThemeColor color;
+}
+
+class IconTheme extends Inherited {
+
+  IconTheme({
+    String key,
+    this.data,
+    Widget child
+  }) : super(key: key, child: child) {
+    assert(data != null);
+    assert(child != null);
+  }
+
+  final IconThemeData data;
+
+  static IconThemeData of(Component component) {
+    IconTheme result = component.inheritedOfType(IconTheme);
+    return result == null ? null : result.data;
+  }
+
+  bool syncShouldNotify(IconTheme old) => data != old.data;
+
+}