Line Height not calculated correctly inside a div

When creating a div with the follow class:
`.divClass{
height: 40px;
line-height: 40px;
}`
The text inside the div should appear to be centered vertically. Currently in HTML-Renderer it renders the text at the very top and only applies the line-height to the next line.

Start by reproducing the supplied div and CSS in HTML-Renderer, then trace how the renderer handles line-height and the first line of text. Done means the text is vertically centered inside a 40px-high div with a 40px line-height, rather than applying the height only to the next line.

索引モデルが issue の本文から書いたものです。