The old API CGScreenRegisterMoveCallback returned update rects in desktop
coordinates [secondary display has an origin != 0,0]. The new CGDisplayStream
API returns update rects in display coordinates [origin == 0,0]. Translating the
update rect based on the display's position on the desktop is now incorrect.
BUG=webrtc:6702
Review-Url: https://codereview.webrtc.org/2496413002
Cr-Commit-Position: refs/heads/master@{#15092}