1- git mv screen_capturer_mac.mm mac/screen_capturer_mac.mm
2- extract class ScreenCapturerMac declaritions to its own header
3- extract static CreateRawScreenCapturer to screen_capturer_darwin.mm
(Using 'darwin' instead of 'mac' allows to make happy the command
git log --follow mac/screen_capturer_mac.mm)
4- git cl format
Bug: webrtc:8652
Change-Id: Ibb13bd5dec61aa9b92c9f5f30fedd0508a727dd9
Reviewed-on: https://webrtc-review.googlesource.com/64680
Commit-Queue: Julien Isorce <julien.isorce@chromium.org>
Reviewed-by: Zijie He <zijiehe@chromium.org>
Cr-Commit-Position: refs/heads/master@{#22620}