Make RtpGenericFrameDescriptor available for E2EE.

This CL makes the RtpGenericFrameDescriptor available in
RTPSenderVideo::SendVideo for encryption and in
RtpVideoStreamReceiver::OnReceivedFrame for decryption.

Bug: webrtc:9361
Change-Id: I5b6d10138c0874657862f103c8c9a2328e6d4a66
Reviewed-on: https://webrtc-review.googlesource.com/102720
Commit-Queue: Philip Eliasson <philipel@webrtc.org>
Reviewed-by: Erik Språng <sprang@webrtc.org>
Reviewed-by: Danil Chapovalov <danilchap@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#24929}

modules/video_coding/packet.cc

@@ -81,4 +81,6 @@ VCMPacket::VCMPacket(const uint8_t* ptr,
   }
 }
 
+VCMPacket::~VCMPacket() = default;
+
 }  // namespace webrtc