Stop using WEBRTC_ macros to detect the target OS.

Bug: 919085
Change-Id: I925f6af3347c6630259b4ef48b15e9b4fbcc1efb
Reviewed-on: https://chromium-review.googlesource.com/c/1397605
Reviewed-by: Harald Alvestrand <hta@chromium.org>
Commit-Queue: Mirko Bonadei <mbonadei@chromium.org>
Cr-Commit-Position: refs/heads/master@{#620750}
2 files changed