Reason for revert:
Broke chromium builder
Original issue's description:
> Use std::unique_ptr<> to pass frame ownership in DesktopCapturer impls.
>
> Previously raw pointers were used for owned DesktopFrame instances.
> Updated all screen and window capturer implementations to use
> std::unique_ptr<>.
>
> Also includes some other cleanups in the capturers:
> - s/NULL/nullptr
> - moved default initializers to class definition.
>
> BUG=webrtc:5950
>
> Committed: https://crrev.com/4a627a8c13554d12412cabb8f751caee6e61ee32
> Cr-Commit-Position: refs/heads/master@{#13032}
TBR=wez@chromium.org
# Skipping CQ checks because original CL landed less than 1 days ago.
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=webrtc:5950
Review-Url: https://codereview.webrtc.org/2030333003
Cr-Commit-Position: refs/heads/master@{#13033}
b4c7b8365d