No functional change. This makes the code more generic
and this reduces the size of screen_capturer_mac.mm
Bug: webrtc:8652
Change-Id: I37743ba385fea5e1b40df3b094bfc321b8d796ae
Reviewed-on: https://webrtc-review.googlesource.com/65082
Commit-Queue: Julien Isorce <julien.isorce@chromium.org>
Commit-Queue: Zijie He <zijiehe@chromium.org>
Reviewed-by: Zijie He <zijiehe@chromium.org>
Cr-Commit-Position: refs/heads/master@{#22684}