Moving oauth code from host to base to allow code sharing between host and client.

remoting/host/setup/mock_oauth_client.h

-// 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.
-
-#ifndef REMOTING_HOST_SETUP_MOCK_OAUTH_CLIENT_H_
-#define REMOTING_HOST_SETUP_MOCK_OAUTH_CLIENT_H_
-
-#include "remoting/host/setup/oauth_client.h"
-
-namespace remoting {
-
-class MockOAuthClient : public OAuthClient {
- public:
-  MockOAuthClient(const std::string& user_email,
-                  const std::string& refresh_token);
-
-  ~MockOAuthClient() override;
-
-  void GetCredentialsFromAuthCode(
-      const gaia::OAuthClientInfo& oauth_client_info,
-      const std::string& auth_code,
-      bool need_user_email,
-      CompletionCallback on_done) override;
-
- private:
-  std::string user_email_;
-  std::string refresh_token_;
-};
-
-}  // namespace remoting
-
-#endif  // REMOTING_HOST_SETUP_MOCK_OAUTH_CLIENT_H_