Change userid from a uint32_t to a string guid

mojo/shell/public/cpp/shell_client.h

 // Copyright 2014 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 MOJO_SHELL_PUBLIC_CPP_SHELL_CLIENT_H_
 #define MOJO_SHELL_PUBLIC_CPP_SHELL_CLIENT_H_
 
 #include <stdint.h>
 #include <string>
 
@@ skipping 15 matching lines @@
   virtual ~ShellClient();
 
   // Called once a bidirectional connection with the shell has been established.
   // |name| is the name used to start the application.
   // |id| is a unique identifier the shell uses to identify this specific
   // instance of the application.
   // |user_id| identifies the user this instance is run as.
   // Called exactly once before any other method.
   virtual void Initialize(Connector* connector,
                           const std::string& name,
-                          uint32_t id,
-                          uint32_t user_id = 0);
+                          const std::string& user_id,
+                          uint32_t id);
 
   // Called when a connection to this client is brokered by the shell. Override
   // to expose services to the remote application. Return true if the connection
   // should succeed. Return false if the connection should be rejected and the
   // underlying pipe closed. The default implementation returns false.
   virtual bool AcceptConnection(Connection* connection);
 
   // Called when ShellConnection's ShellClient binding (i.e. the pipe the
   // Mojo Shell has to talk to us over) is closed. A shell client may use this
   // as a signal to terminate.
   virtual void ShellConnectionLost();
 
  private:
   DISALLOW_COPY_AND_ASSIGN(ShellClient);
 };
 
 }  // namespace mojo
 
 #endif  // MOJO_SHELL_PUBLIC_CPP_SHELL_CLIENT_H_