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

mojo/shell/standalone/context.cc

Index: mojo/shell/standalone/context.cc
diff --git a/mojo/shell/standalone/context.cc b/mojo/shell/standalone/context.cc
index 6cd1ac4e246bd8756076582db5a67fb61fa94efb..a6fcbed7233eb18c57257fbbdacf17c0af5e4d18 100644
--- a/mojo/shell/standalone/context.cc
+++ b/mojo/shell/standalone/context.cc
@@ -164,8 +164,7 @@ void Context::Init(scoped_ptr<InitParams> init_params) {
 
   scoped_ptr<ConnectParams> params(new ConnectParams);
   params->set_source(CreateShellIdentity());
-  params->set_target(
-      Identity("mojo:tracing", std::string(), mojom::kInheritUserID));
+  params->set_target(Identity("mojo:tracing", mojom::kInheritUserID));
   params->set_remote_interfaces(GetProxy(&tracing_remote_interfaces));
   params->set_local_interfaces(std::move(tracing_local_interfaces));
   shell_->Connect(std::move(params));
@@ -238,7 +237,7 @@ void Context::Run(const std::string& name) {
 
   scoped_ptr<ConnectParams> params(new ConnectParams);
   params->set_source(CreateShellIdentity());
-  params->set_target(Identity(name, std::string(), mojom::kRootUserID));
+  params->set_target(Identity(name, mojom::kRootUserID));
   params->set_remote_interfaces(GetProxy(&remote_interfaces));
   params->set_local_interfaces(std::move(local_interfaces));
   shell_->Connect(std::move(params));