Flex / Grid layouts not working on button or fieldset elements
<p>I'm trying to center inner elements of a <code>&lt;button&gt;</code>-tag with flexbox's <code>justify-content: center</code>. But Safari does not center them. I can apply the same style to any other tags and it works as intended (see the <code>&lt;p&gt;</code>-tag). Only the button is left-aligned.</p>

<p>Try Firefox or Chrome and you can see the difference.</p>

<p>Is there any user agent style I have to overwrite? Or any other solution to this problem?</p>

<p><div class="snippet" data-lang="js" data-hide="false" data-console="true" data-babel="false">
<div class="snippet-code">
<pre class="snippet-code-css lang-css prettyprint-override"><code>div {
  display: flex;
  flex-direction: column;
  width: 100%;
}
button, p {
  display: flex;
  flex-direction: row;
  justify-content: center;
}</code></pre>
<pre class="snippet-code-html lang-html prettyprint-override"><code>&lt;div&gt;
  &lt;button&gt;
    &lt;span&gt;Test&lt;/span&gt;
    &lt;span&gt;Test&lt;/span&gt;
  &lt;/button&gt;
  &lt;p&gt;
    &lt;span&gt;Test&lt;/span&gt;
    &lt;span&gt;Test&lt;/span&gt;
  &lt;/p&gt;
&lt;/div&gt;</code></pre>
</div>
</div>
</p>

<p>And a jsfiddle:
<a href="http://jsfiddle.net/z3sfwtn2/2/" rel="noreferrer">http://jsfiddle.net/z3sfwtn2/2/</a></p>