Add new ConnectionEvent API (hide) to send a notification to Telecom

Connection event used to inform Telecom that it should play or stop
the on hold tone. This is used to play or stop a tone when the peer
puts the current call on hold.

BUG=25357778
Change-Id: I2669f8f5062449784a712b9dd28e576326fcc679

telecomm/java/android/telecom/RemoteConnectionService.java

@@ -330,6 +330,13 @@ final class RemoteConnectionService {
                         .setExtras(extras);
             }
         }
+
+        @Override
+        public void onConnectionEvent(String callId, String event) {
+            if (mConnectionById.containsKey(callId)) {
+                findConnectionForAction(callId, "onConnectionEvent").onConnectionEvent(event);
+            }
+        }
     };
 
     private final ConnectionServiceAdapterServant mServant =