<!doctype html>
<head>
<title>line-box-contain:block</title>
<style>
.test { -webkit-line-box-contain: block; line-box-contain: block; font: 64px/1em Ahem; background-color:red; width:6em}
.goodline { color: green; line-height:12 }
</style>
</head>
<body>
You should see a green rectangle below.  If you see any red, the test has failed.

<div class="test">
<span class="goodline">xxxxx</span><div style="display:inline-block; width:1em;height:2em;vertical-align:top;background-color:green"></div><br>
<div style="display:inline-block; width:1em;height:2em;vertical-align:bottom;background-color:green"></div><span class="goodline">xxxxx</span>
</div>