title: Remove Padding on CupertinoSliverNavigationBar
body: <p>I am trying to use <code>CupertinoSliverNavigationBar</code>, actually it's great, but for some reason I can't place the trailing right on the end of navigation bar. I looked up and I (guess, I) found that there's <code>Padding</code> inside it</p>
  
  <p><a href="https://i.stack.imgur.com/XiuTM.jpg" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/XiuTM.jpg" alt="enter image description here"></a></p>
  
  <p>this is my code</p>
  
  <pre><code>   new CupertinoPageScaffold(
          child: new CustomScrollView(
            slivers: &lt;Widget&gt;[
              new CupertinoSliverNavigationBar(
                largeTitle: new Text('Tasks'),
                trailing: new CupertinoButton(
                  child: new Icon(AdditionalCupertinoIcons.compose, size: 32.0),
                  onPressed: () {
                    showDialog(
                        context: context,
                        builder: (BuildContext context) {
                          return new CupertinoAlertDialog();
                        });
                  },
                  padding: EdgeInsets.all(0.0),
                ),
              )
            ],
          ),
        ),
  </code></pre>