Add speech flag to EncodedInfo

The flag indicates if the encoded bitstream is speech or comfort noise.

COAUTHOR=kwiberg@webrtc.org
R=jmarusic@webrtc.org

Review URL: https://webrtc-codereview.appspot.com/42629004

Cr-Original-Commit-Position: refs/heads/master@{#8598}
Cr-Mirrored-From: https://chromium.googlesource.com/external/webrtc
Cr-Mirrored-Commit: c86bbbaa9348b868e94c021426abcc2f5e0144b0
5 files changed