Change userid from a uint32_t to a string guid

ash/mus/sysui_application.cc

 // Copyright 2016 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 "ash/mus/sysui_application.h"
 
 #include "ash/desktop_background/desktop_background_controller.h"
 #include "ash/host/ash_window_tree_host_init_params.h"
 #include "ash/host/ash_window_tree_host_platform.h"
 #include "ash/mus/keyboard_ui_mus.h"
@@ skipping 261 matching lines @@
 
   DISALLOW_COPY_AND_ASSIGN(AshInit);
 };
 
 SysUIApplication::SysUIApplication() {}
 
 SysUIApplication::~SysUIApplication() {}
 
 void SysUIApplication::Initialize(mojo::Connector* connector,
                                   const std::string& url,
-                                  uint32_t id,
-                                  uint32_t user_id) {
+                                  const std::string& user_id,
+                                  uint32_t id) {
   ash_init_.reset(new AshInit());
   ash_init_->Initialize(connector);
 }
 
 bool SysUIApplication::AcceptConnection(mojo::Connection* connection) {
   return true;
 }
 
 }  // namespace sysui
 }  // namespace ash