Revert of Delete method cricket::VideoFrame::Copy. (patchset #7 id:120001 of https://codereview.webrtc.org/2080253002/ )

Reason for revert:
It broke a downstream build by removing VideoFrame::Copy method.

Original issue's description:
> Delete method cricket::VideoFrame::Copy.
>
> Should be unused in Chrome since cl
> https://codereview.chromium.org/2068703002/
>
> TBR=tkchin@webrtc.org,magjed@webrtc.org
> BUG=webrtc:5682
>
> Committed: https://crrev.com/9c00f646f0b3cd33506a1944c7bc6724af041237
> Committed: https://crrev.com/7e4e00d189a5dfac2b463a5100ee65ee2f11ed79
> Cr-Original-Commit-Position: refs/heads/master@{#13236}
> Cr-Commit-Position: refs/heads/master@{#13244}

TBR=pbos@webrtc.org,tkchin@webrtc.org,magjed@webrtc.org,sergeyu@chromium.org,nisse@webrtc.org
# Skipping CQ checks because original CL landed less than 1 days ago.
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=webrtc:5682

Review-Url: https://codereview.webrtc.org/2087923004
Cr-Original-Commit-Position: refs/heads/master@{#13246}
Cr-Mirrored-From: https://chromium.googlesource.com/external/webrtc
Cr-Mirrored-Commit: 123f33cd009606d22cca8b0f4756812406d4580f
1 file changed