mozilla/bedrock — comment on commit 71bae1a6ce401770c12dcb5c1fcf4edb76dba56d
File: templates/base.html line 8
By sgarrity:

The web font includes are intentionally done inline rather than in an external CSS file. This allows the font files to begin loading before the CSS is included. A site_fonts block similar to the site_css block that can have a default and be overridden might be ideal.