Remove padding in Flutter Container > FlatButton : <p>I am looking to remove the default margin of the FlatButton but can't seem to set/override it.</p>

<p><a href="https://i.stack.imgur.com/auKR7.png" rel="noreferrer"><img src="https://i.stack.imgur.com/auKR7.png" alt="buttons with padding"></a></p>

<pre><code>Column(children: &lt;Widget&gt;[
      Container(
          children: [
            FractionallySizedBox(
              widthFactor: 0.6,
              child: FlatButton(
                  color: Color(0xFF00A0BE),
                  textColor: Color(0xFFFFFFFF),
                  child: Text('LOGIN', style: TextStyle(letterSpacing: 4.0)),
                  shape: RoundedRectangleBorder(side: BorderSide.none)))),
      Container(
          margin: const EdgeInsets.only(top: 0.0),
          child: FractionallySizedBox(
              widthFactor: 0.6,
              child: FlatButton(
                  color: Color(0xFF00A0BE),
                  textColor: Color(0xFF525252),
                  child: Text('SIGN UP',
                      style: TextStyle(
                          fontFamily: 'Lato',
                          fontSize: 12.0,
                          color: Color(0xFF525252),
                          letterSpacing: 2.0)))))
    ])
</code></pre>

<p>I've come across things like <code>ButtonTheme</code> and even <code>debugDumpRenderTree()</code> but haven't been able to implement them properly.</p>
