title: How to vertically center differently-sized hintText in TextField?
body: <p>I have a <code>TextField</code> like this, where the input text and the hint text are sized differently.</p>
  <pre><code>TextField(
      style: Theme.of(context).textTheme.subhead.copyWith(
        fontSize: 70.0,
      ),
      decoration: InputDecoration(
        hintText: 'Enter a number',
        hideDivider: true,
        hintStyle: TextStyle(
          color: Colors.grey[500],
          fontSize: 25.0,
        ),
      ),
  );
  </code></pre>
  <p>While the user input text is centered in my parent container, the hintText is not (top has more space than the bottom). Is there a way to vertically center the hint text as well?</p>
  <p>The reason the hint text is not the same size as the input text is that it takes up more space than the green Container has, so it looks like <code>Enter a nu...</code>, which isn't very user friendly. (So alternatively, is there a way to have a newline in the hintText?)</p>
  <p><a href="https://i.stack.imgur.com/7H9zi.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/7H9zi.png" alt="Hint text is smaller so that I can fit it all in the widget" /></a></p>
  <p><a href="https://i.stack.imgur.com/Ap7Jn.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/Ap7Jn.png" alt="Input text is centered" /></a></p>