Bug 857951 - DuT doesn't show 'busy line' screen or play 'busy line' tone.
Merge pull request #9249 from gtorodelvalle/dialer-bug-857951-busy-tone-from-etiennesegonzac-bug-859354-call-waiting-alert

Dialer bug 857951 busy tone from etiennesegonzac bug 859354 call waiting alert (r=etiennesegonzac)