Add ArcAuthService to handle IPC request from ARC

chrome/browser/chromeos/arc/arc_auth_service_impl.cc

+// Copyright 2015 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 "chrome/browser/chromeos/arc/arc_auth_service_impl.h"
+
+#include <utility>
+
+namespace arc {
+
+ArcAuthServiceImpl::ArcAuthServiceImpl() : binding_(this) {
+}
+
+ArcAuthServiceImpl::~ArcAuthServiceImpl() {
+  ArcBridgeService* bridge_service = ArcBridgeService::Get();
+  DCHECK(bridge_service);

[achuithb, 2016/01/04 23:41:59]

You don't need this DCHECK, the line below crashes if bridge_service is null.

You should just do:
ArcBridgeService::Get()->RemoveObserver(this);

[victorhsieh, 2016/01/05 00:39:14]

Done.

+  bridge_service->RemoveObserver(this);
+}
+
+void ArcAuthServiceImpl::StartObservingBridgeServiceChanges() {
+  ArcBridgeService* bridge_service = ArcBridgeService::Get();
+  DCHECK(bridge_service);
+  bridge_service->AddObserver(this);

[achuithb, 2016/01/04 23:41:59]

ArcBridgeService::Get()->AddObserver(this);

[victorhsieh, 2016/01/05 00:39:14]

Done.

+}
+
+void ArcAuthServiceImpl::OnAuthInstanceReady() {
+  ArcBridgeService* bridge_service = ArcBridgeService::Get();
+  DCHECK(bridge_service);
+
+  arc::AuthHostPtr host;
+  binding_.Bind(GetProxy(&host));
+  bridge_service->auth_instance()->Init(std::move(host));

[achuithb, 2016/01/04 23:41:59]

ArcBridgeService::Get()->auth_instance()->Init(std::move(host));

[victorhsieh, 2016/01/05 00:39:14]

Done.

+}
+
+void ArcAuthServiceImpl::GetAuthCode(const GetAuthCodeCallback& callback) {
+  // TODO(victorhsieh): request auth code from LSO.

[achuithb, 2016/01/04 23:41:59]

Please reference a bug here

[victorhsieh, 2016/01/05 00:39:14]

Done.

+  callback.Run(mojo::String("fake auth code from ArcAuthService in Chrome"));
+}
+
+}  // namespace arc