Change userid from a uint32_t to a string guid

mojo/shell/public/interfaces/shell_client.mojom

Index: mojo/shell/public/interfaces/shell_client.mojom
diff --git a/mojo/shell/public/interfaces/shell_client.mojom b/mojo/shell/public/interfaces/shell_client.mojom
index 2dad17c1854d8419fab8dba6634f03c8f3f4fe9e..2af9a1f68ebd9c80a342c1dbc2aa7412f1cf9b2f 100644
--- a/mojo/shell/public/interfaces/shell_client.mojom
+++ b/mojo/shell/public/interfaces/shell_client.mojom
@@ -24,16 +24,16 @@ interface ShellClient {
   //    The resolved name used in the connection request that resulted in this
   //    application being initialized.
   //
-  //  id
-  //    A unique identifier used by the shell to identify this instance.
-  //
   //  user_id
   //    Identifies the user this instance is run as in the shell. This may
   //    differ from the user the application that caused this application to be
   //    instantiated is run as. This will always be a valid user id, never
   //    Shell::kUserInherit.
   //
-  Initialize(Connector connector, string name, uint32 id, uint32 user_id);
+  //  id
+  //    A unique identifier used by the shell to identify this instance.
+  //
+  Initialize(Connector connector, string name, string user_id, uint32 id);
 
   // Called when another application attempts to open a connection to this
   // application. An application implements this method to complete the exchange
@@ -55,7 +55,7 @@ interface ShellClient {
   //    An identifier for the user the source application is run as. This may
   //    differ from the application the target is run as (i.e. the one received
   //    via Initialize() above). This will always be a valid user id, never
-  //    Shell::kUserInherit.
+  //    kInheritUserID.
   //
   //  local_interfaces
   //    A request for an InterfaceProvider by which the source application may
@@ -75,8 +75,8 @@ interface ShellClient {
   //    The resolved name used to complete this connection.
   //
   AcceptConnection(string requestor_name,
+                   string requestor_user_id,
                    uint32 requestor_id,
-                   uint32 requestor_user_id,
                    InterfaceProvider&? local_interfaces,
                    InterfaceProvider? remote_interfaces,
                    array<string> allowed_interfaces,