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

Reason for revert:
Breaks chrome, because a new use of Copy was added in cl https://codereview.chromium.org/2062843003

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
> Cr-Commit-Position: refs/heads/master@{#13236}

TBR=pbos@webrtc.org,tkchin@webrtc.org,magjed@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/2082643004
Cr-Commit-Position: refs/heads/master@{#13238}

webrtc/sdk/objc/Framework/Classes/RTCVideoFrame.mm

@@ -12,8 +12,6 @@
 
 #include <memory>
 
-#include "webrtc/media/engine/webrtcvideoframe.h"
-
 @implementation RTCVideoFrame {
   std::unique_ptr<cricket::VideoFrame> _videoFrame;
   rtc::scoped_refptr<webrtc::VideoFrameBuffer> _i420Buffer;
@@ -107,10 +105,7 @@
   if (self = [super init]) {
     // Keep a shallow copy of the video frame. The underlying frame buffer is
     // not copied.
-    _videoFrame.reset(new cricket::WebRtcVideoFrame(
-        nativeFrame->video_frame_buffer(),
-        nativeFrame->rotation(),
-        nativeFrame->timestamp_us()));
+    _videoFrame.reset(nativeFrame->Copy());
   }
   return self;
 }