Change userid from a uint32_t to a string guid

mash/shell/shell_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/shell/shell_application_delegate.h"
 
 #include "base/bind.h"
 #include "base/command_line.h"
 #include "mojo/shell/public/cpp/connection.h"
 #include "mojo/shell/public/cpp/connector.h"
 
 namespace mash {
 namespace shell {
 
 ShellApplicationDelegate::ShellApplicationDelegate()
     : connector_(nullptr), screen_locked_(false) {}
 
 ShellApplicationDelegate::~ShellApplicationDelegate() {}
 
 void ShellApplicationDelegate::Initialize(mojo::Connector* connector,
                                           const std::string& url,
-                                          uint32_t id,
-                                          uint32_t user_id) {
+                                          const std::string& user_id,
+                                          uint32_t id) {
   connector_ = connector;
   StartBrowserDriver();
   StartWindowManager();
   StartSystemUI();
   StartQuickLaunch();
 }
 
 bool ShellApplicationDelegate::AcceptConnection(mojo::Connection* connection) {
   connection->AddInterface<mojom::Shell>(this);
   return true;
@@ skipping 82 matching lines @@
   if (connection) {
     connection->SetRemoteInterfaceProviderConnectionErrorHandler(
         restart_callback);
     connection->AddInterface<mojom::Shell>(this);
     connections_[url] = std::move(connection);
   }
 }
 
 }  // namespace shell
 }  // namespace main