Added unit tests for getCredentialsFromAuthCode.

remoting/host/setup/mock_oauth_client.cc

Index: remoting/host/setup/mock_oauth_client.cc
diff --git a/remoting/host/setup/mock_oauth_client.cc b/remoting/host/setup/mock_oauth_client.cc
new file mode 100644
index 0000000000000000000000000000000000000000..d748744456368059c4f01bea11a62fa6497dc896
--- /dev/null
+++ b/remoting/host/setup/mock_oauth_client.cc
@@ -0,0 +1,20 @@
+// 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 "remoting/host/setup/mock_oauth_client.h"
+
+namespace remoting {
+
+MockOAuthClient::~MockOAuthClient() {
+}
+
+void MockOAuthClient::GetCredentialsFromAuthCode(
+    const gaia::OAuthClientInfo& oauth_client_info,
+    const std::string& auth_code,
+    CompletionCallback on_done) {
+
+  on_done.Run(user_email_, refresh_token_);
+}
+
+}  // namespace remoting