www/chromium: add CUPS option

[leres]

Summary

Proposed commit message:

Add a CUPS option to disable cups support and remove the
dependency on print/cups. This includes a patch from cpm@
that solves an undefined linker reference that occurs when
cups is disabled. Since chromium does not support printing
without cups enabling this option also disables printing and
print previews. 

PR: 226505
Reviewed by: ?
Approved by: ?
Differential Revision: ?

[matthew]

This looks OK, on the face of it, although I'm having some (hopefully temporary) local troubles getting a test build to work.
Are you in contact with the chromium@ developers? According to https://wiki.freebsd.org/Chromium that's [e-mail] or [e-mail]:
it might be worth adding them as reviewers.

[matthew]

Ah -- I see cpm@ has commented on the bugzilla PR. Remember to add him to the Approved by: line when you commit.