Change userid from a uint32_t to a string guid

mash/example/views_examples/views_examples_application_delegate.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 "mash/example/views_examples/views_examples_application_delegate.h"
 
 #include "mojo/shell/public/cpp/connection.h"
 #include "mojo/shell/public/cpp/connector.h"
 #include "ui/views/examples/example_base.h"
 #include "ui/views/examples/examples_window.h"
 #include "ui/views/mus/aura_init.h"
 #include "ui/views/mus/window_manager_connection.h"
 
 ViewsExamplesApplicationDelegate::ViewsExamplesApplicationDelegate() {}
 
 ViewsExamplesApplicationDelegate::~ViewsExamplesApplicationDelegate() {
 }
 
 void ViewsExamplesApplicationDelegate::Initialize(mojo::Connector* connector,
                                                   const std::string& url,
-                                                  uint32_t id,
-                                                  uint32_t user_id) {
+                                                  const std::string& user_id,
+                                                  uint32_t id) {
   tracing_.Initialize(connector, url);
   aura_init_.reset(new views::AuraInit(connector, "views_mus_resources.pak"));
 
   views::WindowManagerConnection::Create(connector);
 
   views::examples::ShowExamplesWindow(views::examples::DO_NOTHING_ON_CLOSE,
                                       nullptr, nullptr);
 }
 
 bool ViewsExamplesApplicationDelegate::AcceptConnection(
     mojo::Connection* connection) {
   return false;
 }