Use the platform=linux code path for other Unix-like platforms (FreeBSD and OpenBSD) as well, not just OS(LINUX) - with the exception of MacOS.

As a side benefit this change removes code that was not tested by any of the existing bots.

Review URL: https://chromiumcodereview.appspot.com/23537045

git-svn-id: svn://svn.chromium.org/blink/trunk@158120 bbb929c8-8fbe-4397-9dbb-9b2b20218538