Prior to this fix, the line-height of heading elements is set to 1.2em.
This leads to an issue when the font-size of heading anchor element is
reduced as shown in the following example:
<!DOCTYPE html>
<html lang="en">
<head>
<title>Test</title>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, intial-scale=1">
<link rel="stylesheet" href="sp.css">
<style>
h2 {background: lightblue}
div {background: orange; display: inline-block}
p {background: lightgreen}
.b a:empty {font-size: small}
</style>
</head>
<body>
<div class="a"><h2>Foo<a href="#"></a></h2><p>Bar</p></div>
<div class="b"><h2>Foo<a href="#"></a></h2><p>Bar</p></div>
</body>
</html>
The smaller font-size for the anchor element within class "b" leads to a
larger overall size for the heading element as explained at
<https://stackoverflow.com/a/21575694>. Set the line-height of heading
elements to the unitless number 1.2 to resolve this issue.
