Reason for revert:
Deleting scopedptrcollection.h broke an internal project.
Original issue's description:
> Delete class ScopedPtrCollection. Replaced with vector of unique_ptr.
>
> BUG=None
>
> Review-Url: https://codereview.webrtc.org/2808463002
> Cr-Commit-Position: refs/heads/master@{#17605}
> Committed: 188596f20f
TBR=pthatcher@webrtc.org,kwiberg@webrtc.org
# Skipping CQ checks because original CL landed less than 1 days ago.
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=None
Review-Url: https://codereview.webrtc.org/2812553002
Cr-Commit-Position: refs/heads/master@{#17607}
Name: WebRTC URL: http://www.webrtc.org Version: 90 License: BSD License File: LICENSE Description: WebRTC provides real time voice and video processing functionality to enable the implementation of PeerConnection/MediaStream. Third party code used in this project is described in the file LICENSE_THIRD_PARTY.