adding default rates
adding default rates

Cr-Mirrored-From: https://chromium.googlesource.com/external/webrtc
Cr-Mirrored-Commit: 0b626725761cd89d4422f4538939613cbe5d1f27

sippet/talk,sippet/talk,sippet/talk,sippet/talk,sippet/talk