We don't support pre-lion, so all this screencapture code is unnecessary.
This also enables us to delete some code from rtc_base/macutils
Bug: webrtc:6424
Change-Id: I4ef068e8d7b48de9370feee51399033a4d1ae1c3
Reviewed-on: https://webrtc-review.googlesource.com/3420
Reviewed-by: Niels Moller <nisse@webrtc.org>
Reviewed-by: Tommi <tommi@webrtc.org>
Commit-Queue: Kári Helgason <kthelgason@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#20104}