chrome/browser/resources/intro/lacros_app.html

<style>
:host {
  align-items: center;
  display: flex;
  flex-direction: column;
  height: 100%;
  justify-content: space-evenly;
  width: 100%;
}
</style>

<h1>Welcome to Lacros</h1>

<cr-button on-click="onContinueWithAccountClick_">Continue</cr-button>