Essentially a copy of https://codereview.chromium.org/2299953002/
plus changes to WebRTC's license, changed OWNERS and additional
MB updates up to Chromium revision http://crrev.com/f1e2718a3ff.
The PRESUBMIT.py check was updated to use the existing
webrtc/build/mb_config.pyl to avoid breaking bots (that have
this path hardcoded).
This replaces the previously symlinked MB, which already
runs validation of the WebRTC configs as part of
webrtc/build/PRESUBMIT.py.
BUG=chromium:664425
NOTRY=True
TESTED=Ran:
tools/mb/mb.py gen -m client.webrtc -b 'Mac64 Release' --config-file webrtc/build/mb_config.pyl --isolate-map-file=webrtc/build/gn_isolate_map.pyl --gyp-script=webrtc/build/gyp_webrtc.py //out/Release
Review-Url: https://codereview.webrtc.org/2306163002
Cr-Commit-Position: refs/heads/master@{#15068}
