Change userid from a uint32_t to a string guid

mash/quick_launch/quick_launch_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 "mash/quick_launch/quick_launch_application.h"
 
 #include "base/macros.h"
 #include "base/strings/string_util.h"
 #include "base/strings/utf_string_conversions.h"
 #include "mojo/public/c/system/main.h"
@@ skipping 72 matching lines @@
   std::vector<scoped_ptr<mojo::Connection>> connections_;
 
   DISALLOW_COPY_AND_ASSIGN(QuickLaunchUI);
 };
 
 QuickLaunchApplication::QuickLaunchApplication() {}
 QuickLaunchApplication::~QuickLaunchApplication() {}
 
 void QuickLaunchApplication::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::Widget* window = views::Widget::CreateWindowWithBounds(
       new QuickLaunchUI(connector), gfx::Rect(10, 640, 0, 0));
   window->Show();
 }
 
 bool QuickLaunchApplication::AcceptConnection(mojo::Connection* connection) {
   return true;
 }
 
 }  // namespace quick_launch
 }  // namespace mash