Linux: Depend on liberation-fonts package. (try 2)

Without these fonts, text in the built-in PDF viewer may not display
correctly.

Unfortunately we can only do this for the .deb packages at the moment.
There's no common liberation-fonts package for RPMs. See
https://crbug.com/519322.

BUG=369991

Review URL: https://codereview.chromium.org/1274043004

Cr-Commit-Position: refs/heads/master@{#342854}
2 files changed