InterClue is a browser extension for Firefox, which allows you to get a preview and summary of the linked page, while hovering on a link. This is useful for link-heavy pages like you have in Trac, or when you want to quickly get more details about tickets from a ticket query (see #10383).
Chrome has a similar plugin.
You can see in the image that it has special support for Trac. The
Lines Modified and
Total Lines Altered are displayed in the overlay; the count of lines is not exact though.