Split C++ class from macro overrides to fix Chromium build

BUG=chromium:468375
TBR=kjellander@webrtc.org,ajm@webrtc.org

Review URL: https://webrtc-codereview.appspot.com/51409004

Cr-Original-Commit-Position: refs/heads/master@{#8786}
Cr-Mirrored-From: https://chromium.googlesource.com/external/webrtc
Cr-Mirrored-Commit: c4709a29306a21f5272c1db6f394f47b64a849b5
3 files changed