docs: Update Fedora dependencies in Linux build instructions.

This CL points to an updated method for installing the fonts needed by
LayoutTests on Fedora. It also adds ixorg-x11-server-Xvfb to the list of
required packages, as Blink's run-webkit-tests tool requires xvfb.

Bug: 
Change-Id: I8bf9a1539066880ca0ea450786847a5126f9cefb
Reviewed-on: https://chromium-review.googlesource.com/764861
Reviewed-by: Dirk Pranke <dpranke@chromium.org>
Commit-Queue: Victor Costan <pwnall@chromium.org>
Cr-Commit-Position: refs/heads/master@{#516016}
1 file changed