title: How to center the title of an appbar
body: <p>I'm trying to center the title text in an app bar that has both a leading and trailing actions.</p>
  <pre><code>@override
  Widget build(BuildContext context) {
    final menuButton = new PopupMenuButton&lt;int&gt;(
      onSelected: (int i) {},
      itemBuilder: (BuildContext ctx) {},
      child: new Icon(
        Icons.dashboard,
      ),
    );
  
    return new Scaffold(
      appBar: new AppBar(
        // Here we take the value from the MyHomePage object that
        // was created by the App.build method, and use it to set
        // our appbar title.
        title: new Text(widget.title, textAlign: TextAlign.center),
        leading: new IconButton(
            icon: new Icon(Icons.accessibility),
            onPressed: () {},
        ),
        actions: [
          menuButton,
        ],
      ),
      body: new Center(
        child: new Text(
          'Button tapped $_counter time${ _counter == 1 ? '' : 's' }.',
        ),
      ),
      floatingActionButton: new FloatingActionButton(
        onPressed: _incrementCounter,
        tooltip: 'Increment',
        child: new Icon(Icons.add),
      ), // This trailing comma makes auto-formatting nicer for build methods.
    );
  }
  </code></pre>
  <p>This works well except the title is aligned on the left as is shown in this picture:</p>
  <p><img src="https://i.stack.imgur.com/r6WIOm.png" alt="TITLE TO THE LEFT" /></p>
  <p>As I try to include the title in the center, it appears that it's too much to the left:</p>
  <pre><code>@override
  Widget build(BuildContext context) {
    final menuButton = new PopupMenuButton&lt;int&gt;(
      onSelected: (int i) {},
      itemBuilder: (BuildContext ctx) {},
      child: new Icon(
        Icons.dashboard,
      ),
    );
  
    return new Scaffold(
      appBar: new AppBar(
        // Here we take the value from the MyHomePage object that
        // was created by the App.build method, and use it to set
        // our appbar title.
        title: new Center(child: new Text(widget.title, textAlign: TextAlign.center)),
        leading: new IconButton(
            icon: new Icon(Icons.accessibility),
            onPressed: () {},
        ),
        actions: [
          menuButton,
        ],
      ),
      body: new Center(
        child: new Text(
          'Button tapped $_counter time${ _counter == 1 ? '' : 's' }.',
        ),
      ),
      floatingActionButton: new FloatingActionButton(
        onPressed: _incrementCounter,
        tooltip: 'Increment',
        child: new Icon(Icons.add),
      ), // This trailing comma makes auto-formatting nicer for build methods.
    );
  }
  </code></pre>
  <p><img src="https://i.stack.imgur.com/P08Pnm.png" alt="TITLE NOT WELL CENTERED" /></p>
  <p>I would love a solution to get the title text centered perfectly between the 2 icons.</p>