Add NetEqInput::PacketData::ToString method

This new method prints information about the packet.

BUG=webrtc:7467

Review-Url: https://codereview.webrtc.org/2844283002
Cr-Original-Commit-Position: refs/heads/master@{#17922}
Cr-Mirrored-From: https://chromium.googlesource.com/external/webrtc
Cr-Mirrored-Commit: 7a38fd2628eb6711a9adae9ce93b41c85f1521b0
4 files changed