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

mash/example/window_type_launcher/window_type_launcher.cc

Index: mash/example/window_type_launcher/window_type_launcher.cc
diff --git a/mash/example/window_type_launcher/window_type_launcher.cc b/mash/example/window_type_launcher/window_type_launcher.cc
index 141bb3fd48eaa1abbe7019663c89273665f59524..106dfc10b08040527d62a07f33395b0b4f4378d1 100644
--- a/mash/example/window_type_launcher/window_type_launcher.cc
+++ b/mash/example/window_type_launcher/window_type_launcher.cc
@@ -356,8 +356,7 @@ WindowTypeLauncher::WindowTypeLauncher() {}
 WindowTypeLauncher::~WindowTypeLauncher() {}
 
 void WindowTypeLauncher::Initialize(mojo::Connector* connector,
-                                    const std::string& url,
-                                    const std::string& user_id,
+                                    const mojo::Identity& identity,
                                     uint32_t id) {
   aura_init_.reset(new views::AuraInit(connector, "views_mus_resources.pak"));