Refactor ChannelAuthenticator so that it can be used with Authenticator.

remoting/protocol/jingle_session_unittest.cc

Index: remoting/protocol/jingle_session_unittest.cc
diff --git a/remoting/protocol/jingle_session_unittest.cc b/remoting/protocol/jingle_session_unittest.cc
index f96f03876e13a8a3cb5090a47027355596b8e454..decef783d1be2e17bd1624b5b58f1c3833980b43 100644
--- a/remoting/protocol/jingle_session_unittest.cc
+++ b/remoting/protocol/jingle_session_unittest.cc
@@ -239,7 +239,7 @@ class JingleSessionTest : public testing::Test {
         EXPECT_CALL(host_connection_callback_,
                     OnStateChange(Session::CONNECTED_CHANNELS))
             .Times(AtMost(1));
-        // Expect that the connection will be closed eventually.
+        // Expect that the connection will fail.
         EXPECT_CALL(host_connection_callback_,
                     OnStateChange(Session::FAILED))
             .Times(1)