Low quality "Build on GitHub" icons

[atouchet]

From the "Build on GitHub" section of the GitHub homepage. The icons look noticeably worse in Servo than in other browsers. Also strangely they appear to be slightly off-centre as well. Possibly the same issue as #11960.

Image of the issue (Firefox top, Servo bottom):

Tested in Windows 10.

[jdm]

@glennw Could this be an issue in WR?

[atouchet]

There is a second example of this issue on https://github.com/features as well.

Edit: There are a number of examples throughout GitHub.

[atouchet]

Click for full resolution.

This is slightly improved in the latest nightly build but most of the icons are still bad looking. The only one that is noticeably different is Codeship and that now looks blurrier than in Firefox. @glennw is this due to servo/webrender#2408? I noticed that Codeship is the only icon there larger than 512 x 512 (https://assets-cdn.github.com/images/modules/site/integrators/codeship.png).