Change userid from a uint32_t to a string guid

mash/quick_launch/quick_launch_application.h

 // 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.
 
 #ifndef MASH_QUICK_LAUNCH_QUICK_LAUNCH_APPLICATION_H_
 #define MASH_QUICK_LAUNCH_QUICK_LAUNCH_APPLICATION_H_
 
 #include "base/macros.h"
 #include "base/memory/scoped_ptr.h"
 #include "mojo/services/tracing/public/cpp/tracing_impl.h"
 #include "mojo/shell/public/cpp/shell_client.h"
 
 namespace views {
 class AuraInit;
 }
 
 namespace mash {
 namespace quick_launch {
 
 class QuickLaunchApplication : public mojo::ShellClient {
  public:
   QuickLaunchApplication();
   ~QuickLaunchApplication() override;
 
  private:
   // mojo::ShellClient:
   void Initialize(mojo::Connector* connector,
                   const std::string& url,
-                  uint32_t id,
-                  uint32_t user_id) override;
+                  const std::string& user_id,
+                  uint32_t id) override;
   bool AcceptConnection(mojo::Connection* connection) override;
 
   mojo::TracingImpl tracing_;
   scoped_ptr<views::AuraInit> aura_init_;
 
   DISALLOW_COPY_AND_ASSIGN(QuickLaunchApplication);
 };
 
 }  // namespace quick_launch
 }  // namespace mash
 
 #endif  // MASH_QUICK_LAUNCH_QUICK_LAUNCH_APPLICATION_H_