Correctly handle the error case where the CodecId has a negative value
Correctly handle the error case where the CodecId has a negative value

Negative values should be treated the same as too-large positive values: by returning an empty Maybe.

TBR=henrik.lundin@webrtc.org

Review URL: https://codereview.webrtc.org/1407383010

Cr-Original-Commit-Position: 972c6d2dc6dd5efdad1377c0d224e03eb8f276f7@{#10509}
Cr-Mirrored-From: https://chromium.googlesource.com/external/webrtc
Cr-Mirrored-Commit: 98cc88c87354c96a88cebbd7b803815b4ebeea95

aleonliao/webrtc-trunk,jchavanton/webrtc,jchavanton/webrtc,aleonliao/webrtc-trunk,Alkalyne/webrtctrunk,Alkalyne/webrtctrunk,jchavanton/webrtc,aleonliao/webrtc-trunk,jchavanton/webrtc,jchavanton/webrtc,Alkalyne/webrtctrunk,Alkalyne/webrtctrunk,aleonliao/webrtc-trunk,aleonliao/webrtc-trunk,jchavanton/webrtc,jchavanton/webrtc,Alkalyne/webrtctrunk,aleonliao/webrtc-trunk,Alkalyne/webrtctrunk,Alkalyne/webrtctrunk,Alkalyne/webrtctrunk