Rationalize Dart mojo and sky package structure

sky/framework/components/drawer_header.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 '../theme/colors.dart';
-import '../theme/view_configuration.dart';
-
-class DrawerHeader extends Component {
-  static final Style _style = new Style('''
-    height: ${140 + kStatusBarHeight}px;
-    background-color: ${BlueGrey[50]};
-    border-bottom: 1px solid #D1D9E1;
-    padding-bottom: 7px;
-    margin-bottom: 8px;'''
-  );
-
-  static final FlexBoxParentData _spacerParentData = new FlexBoxParentData()..flex = 1;
-
-  static final Style _labelStyle = new Style('''
-    padding: 0 16px;'''
-  );
-
-  List<UINode> children;
-
-  DrawerHeader({ Object key, this.children }) : super(key: key);
-
-  UINode build() {
-    return new FlexContainer(
-      direction: FlexDirection.Column,
-      style: _style,
-      children: [
-        new ParentDataNode(
-          new Container(key: 'Spacer'),
-          _spacerParentData
-        ),
-        new Container(
-          key: 'Label',
-          style: _labelStyle,
-          children: children
-        )
-      ]
-    );
-  }
-}