title: Add Indicator on top of TabBar in Flutter
body: <p>Like this one:</p>
  
  <p><a href="https://i.stack.imgur.com/CgyFj.jpg" rel="noreferrer"><img src="https://i.stack.imgur.com/CgyFj.jpg" alt="enter image description here"></a></p>
  
  <p>Below code will add Indicator bottom of TabBar:</p>
  
  <pre><code>  DefaultTabController(
      length: 2,
      child : new TabBar(
        labelColor: Colors.purple,
        indicatorColor: Colors.purple,
        indicatorSize: TabBarIndicatorSize.label,
        unselectedLabelColor: Colors.black,
      tabs: [
          new Tab(icon: Icon(Icons.chrome_reader_mode),),
          new Tab(icon: Icon(Icons.clear_all),),
      ]),
    );
  </code></pre>
  
  <p>But I need <code>Indicator</code> on top of <code>TabBar</code>. I don't think it's a great idea to build a custom tab bar because, I don't want to do lot of works for this simple thing.</p>