Remove old Authentication code that we don't use or need.

remoting/proto/auth.proto

-// Copyright (c) 2010 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.
-
-// Messages related to Client/Host Mutual Authentication and Local Login.
-
-syntax = "proto2";
-
-option optimize_for = LITE_RUNTIME;
-
-package remoting.protocol;
-
-// Represents the data used in generating the client auth token during session
-// initiation.
-message ClientAuthToken {
-  optional string host_full_jid = 1;
-  optional string client_full_jid = 2;
-
-  // A short-lived OAuth token identifying the client to the host.
-  optional string client_oauth_token = 3;
-}
-
-// There can be more challenge types later
-enum CredentialType {
-  PASSWORD = 0;
-}
-
-message LocalLoginCredentials {
-  optional CredentialType type = 1;
-  optional string username = 2;
-  optional bytes credential = 3;
-}
-
-message LocalLoginStatus {
-  optional bool success = 1;
-
-  // Only populated if success is set to false.
-  optional int32 tries_remaining = 2 [default = 0];
-  optional string error_info = 3;
-}
-
-// Sent from the Host to the Client.  This is the first message after
-// channels are established.
-message LocalLoginProperties {
-  repeated CredentialType supported_credential_types = 1;
-
-  // Used to generate the bank style anti-phishing image.
-  // This info is stored only on the host.
-  optional bytes antiphish_image = 2;
-  optional bytes antiphish_text = 3;
-}
-
-// Sent from Client to Host.  This consists of both the login attempt,
-// and any session configuration information.
-message BeginSessionRequest {
-  optional LocalLoginCredentials credentials = 1;
-}
-
-// Sent from Host to Client.  Replies with login success, and
-// final client configuration.
-message BeginSessionResponse {
-  optional LocalLoginStatus login_status = 1;
-}