Example
Filled
Markup
<div class="infieldInputGroup">
<label for="id">Label</label>
<div class="inputGroup ">
<input type="text" id="id" />
</div>
</div><br/>
<strong>Filled</strong><br/><br/>
<div class="infieldInputGroup is-filled">
<label for="id">Label</label>
<div class="inputGroup ">
<input type="text" id="id" value="Text" />
</div>
</div>
Source:
build/doc/doc.css
, line 10967