<!DOCTYPE html>
<style>
  @import "resources/height-keyword-classes.css";

  .container {
    display: -webkit-flex;
    display: flex;
    -webkit-flex-direction: column;
    flex-direction: column;

    border: 2px solid blue;
  }

  .item {
    height: 1px;
    border: 2px solid red;
    -webkit-flex: 1;
    flex: 1;
  }
</style>

<div class="container">
  <div class="item min-height-min-content">
    Line 1<br>
    Line 2
  </div>
</div>

<div class="container">
  <div class="item min-height-min-content">
    Line 1
  </div>
  <div class="item min-height-min-content">
    Line 1<br>
    Line 2
  </div>
</div>