Add a instance groups to Connect(), and introduce an Identity struct.

mojo/shell/public/interfaces/shell.mojom

Index: mojo/shell/public/interfaces/shell.mojom
diff --git a/mojo/shell/public/interfaces/shell.mojom b/mojo/shell/public/interfaces/shell.mojom
index f20b87ce6ca7d9cb3340432e26148cb1ab9389e9..1076127c5b029ef26dddce751dbd521772859134 100644
--- a/mojo/shell/public/interfaces/shell.mojom
+++ b/mojo/shell/public/interfaces/shell.mojom
@@ -9,8 +9,7 @@ import "mojo/shell/public/interfaces/shell_client_factory.mojom";
 
 struct InstanceInfo {
   uint32 id;
-  string name;
-  string qualifier;
+  Identity identity;
   uint32 pid;
 };
 
@@ -67,8 +66,7 @@ interface Shell {
   // code, see connector.mojom for definitions) the status of the instance
   // creation.
   CreateInstance(ShellClientFactory factory,
-                 string name,
-                 string user_id,
+                 Identity target,
                  CapabilityFilter filter,
                  PIDReceiver& pid_receiver) => (ConnectResult result);