This refactoring helps to reduce unnecessary memcpy calls on the receive side. This CL replaces |uint8 data[IP_PACKET_SIZE]| with |rtc::CopyOnWriteBuffer data| in Packet class, removes |length| field there, and does necessary changes. This is a reland of these two CLs with fixes: https://webrtc-review.googlesource.com/c/src/+/144942 https://webrtc-review.googlesource.com/c/src/+/144881 Bug: webrtc:10750 Change-Id: I76f6dee5a57ade59942ea2822ca4737edfe6438b Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/145332 Commit-Queue: Ilya Nikolaevskiy <ilnik@webrtc.org> Reviewed-by: Rasmus Brandt <brandtr@webrtc.org> Reviewed-by: Stefan Holmer <stefan@webrtc.org> Cr-Commit-Position: refs/heads/master@{#29035}