[cast_channel] Clean up CastSocketImpl ctor parameters

components/cast_channel/cast_channel_enum.cc

 // Copyright 2017 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "components/cast_channel/cast_channel_enum.h"
 
 #include "base/logging.h"
 
 namespace cast_channel {
 
@@ skipping 25 matching lines @@
     CAST_CHANNEL_TYPE_TO_STRING(ChannelError::INVALID_CHANNEL_ID);
     CAST_CHANNEL_TYPE_TO_STRING(ChannelError::CONNECT_TIMEOUT);
     CAST_CHANNEL_TYPE_TO_STRING(ChannelError::PING_TIMEOUT);
     CAST_CHANNEL_TYPE_TO_STRING(ChannelError::UNKNOWN);
   }
   NOTREACHED() << "Unknown channel_error "
                << ChannelErrorToString(channel_error);
   return "Unknown channel_error";
 }
 
-std::string ChannelAuthTypeToString(ChannelAuthType channel_auth) {
-  switch (channel_auth) {
-    CAST_CHANNEL_TYPE_TO_STRING(ChannelAuthType::NONE);
-    CAST_CHANNEL_TYPE_TO_STRING(ChannelAuthType::SSL_VERIFIED);
-  }
-  NOTREACHED() << "Unknown channel_auth "
-               << ChannelAuthTypeToString(channel_auth);
-  return "Unknown channel_auth";
-}
-
 }  // namespace cast_channel