www/chromium: update to 51.0.2704.84
A lot of patch files are renamed in this update.
Submitted by: Timothy Vaccarelli
Obtained from: https://github.com/LeFroid/
MFH: 2016Q2
Security: http://vuxml.freebsd.org/freebsd/c039a761-2c29-11e6-8912-3065ec8fd3ec.html
Security: http://vuxml.freebsd.org/freebsd/1a6bbb95-24b8-11e6-bd31-3065ec8fd3ec.html
Security: http://vuxml.freebsd.org/freebsd/4dfafa16-24ba-11e6-bd31-3065ec8fd3ec.html
Security: http://vuxml.freebsd.org/freebsd/7da1da96-24bb-11e6-bd31-3065ec8fd3ec.html
Security: http://vuxml.freebsd.org/freebsd/6d8505f0-0614-11e6-b39c-00262d5ed8ee.html