Created attachment 726104 [details]
Screenshot of reddit.com, with Dev Tools open to see which fonts are used.

## Overview

On some websites, text rendered in small point sizes looks ugly, there is no
anti-aliasing. See screenshot attached.

## Steps to reproduce

1.  Go to https://reddit.com, or German news website http://www.tagesspiegel.de

There are certainly more websites affected.

## Actual result

Rendered text looks ugly.

## Expected result

Text is rendered more smoothly, similar to how it works on most websites.

## Build and hardware

USB/DVD install on 64bit laptop, updated to build 0251.

## Additional information

On most websites, text looks fine.

When forcing a certain font in the Firefox settings, the rendering using that
font also looks fine (tested with Source [Sans|Serif|Code] Pro).