Revert "rtc::Buffer: Remove backwards compatibility band-aids"

This reverts commit 9e1a6d7c236c9a8a322bef54d4ec2a087e5baa07, because
Chromium for Android still isn't happy with it.

TBR=tommi@webrtc.org

Review URL: https://webrtc-codereview.appspot.com/49869004

Cr-Commit-Position: refs/heads/master@{#9122}
4 files changed