Added video_coding::EncodedFrame copy ctor.

Bug: none
Change-Id: I45272e81509741dc022d613758466ad0f8de7a31
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/143160
Reviewed-by: Stefan Holmer <stefan@webrtc.org>
Commit-Queue: Philip Eliasson <philipel@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#28333}

modules/video_coding/encoded_frame.cc

@@ -30,6 +30,8 @@ VCMEncodedFrame::VCMEncodedFrame()
   _codecSpecificInfo.codecType = kVideoCodecGeneric;
 }
 
+VCMEncodedFrame::VCMEncodedFrame(const VCMEncodedFrame&) = default;
+
 VCMEncodedFrame::~VCMEncodedFrame() {
   Reset();
 }