Rationalize Dart mojo and sky package structure

sky/framework/components/scaffold.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 '../fn.dart';
-import '../layout.dart';
-import 'drawer.dart';
-import 'floating_action_button.dart';
-import 'package:sky/framework/theme/typography.dart' as typography;
-
-class Scaffold extends Component {
-  static final Style _style = new Style('''
-    ${typography.typeface};
-    ${typography.black.body1};''');
-
-  static final Style _mainStyle = new Style('''
-    height: -webkit-fill-available;''');
-
-  static final FlexBoxParentData _contentParentData = new FlexBoxParentData()..flex = 1;
-
-  static final Style _fabStyle = new Style('''
-    position: absolute;
-    bottom: 16px;
-    right: 16px;''');
-
-  static final Style _drawerStyle = new Style('''
-    position: absolute;
-    top: 0;
-    left: 0;
-    bottom: 0;
-    right: 0;''');
-
-  UINode header;
-  UINode content;
-  FloatingActionButton fab;
-  Drawer drawer;
-  List<UINode> overlays;
-
-  Scaffold({
-    Object key,
-    this.header,
-    this.content,
-    this.fab,
-    this.drawer,
-    this.overlays
-  }) : super(key: key);
-
-  UINode build() {
-    List<UINode> children = [
-      new FlexContainer(
-        key: 'Main',
-        direction: FlexDirection.Column,
-        style: _mainStyle,
-        children: [header, new ParentDataNode(content, _contentParentData)])
-    ];
-
-    if (fab != null)
-      children.add(new StyleNode(fab, _fabStyle));
-
-    if (drawer != null)
-      children.add(new StyleNode(drawer, _drawerStyle));
-
-    if (overlays != null)
-      children.addAll(overlays);
-
-    return new Container(style: _style, children: children);
-  }
-}