Throwing some more info here, this is the NaCl whitelist, looks like it was originally added Feb last year [1]. There's a discussion on Chromium Code Reviews here [2], and an issue on the project itself here [3]

The original commit includes the comment 'We should remove this code when PNaCl ships' which got removed somewhere along the way.

[1] http://src.chromium.org/viewvc/chrome/trunk/src/chrome/rende...

[2] https://codereview.chromium.org/9368046

[3] https://code.google.com/p/chromium/issues/detail?id=113668