chrome/browser/resources/settings/controls/settings_textarea.html

<style include="cr-hidden-style cr-input-style cr-shared-style">
  textarea {
    display: block;
    resize: none;
  }

  #input-container {
    background-color: var(--cr-input-background-color);
  }

  #underline {
    position: static;
  }
</style>
<div id="label" class="cr-form-field-label" hidden="[[!label]]">
  [[label]]
</div>
<div id="input-container">
  <!-- The textarea is limited to |rows| height. If the content exceeds the
       bounds, it scrolls by default. No space or comments are allowed
       before the closing tag. -->
  <textarea id="input" autofocus="[[autofocus]]" rows="[[rows]]"
      value="{{value::input}}" aria-label$="[[label]]"
      on-focus="onInputFocusChange_" on-blur="onInputFocusChange_"
      on-change="onInputChange_" disabled="[[disabled]]"></textarea>
  <div id="underline"></div>
</div>