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

mash/browser_driver/browser_driver_application_delegate.h

Index: mash/browser_driver/browser_driver_application_delegate.h
diff --git a/mash/browser_driver/browser_driver_application_delegate.h b/mash/browser_driver/browser_driver_application_delegate.h
index 03d67d38949c5b16c763795fc4cbfa9c4b080388..2d722f43203764e451228d6ad74a5946e53770f6 100644
--- a/mash/browser_driver/browser_driver_application_delegate.h
+++ b/mash/browser_driver/browser_driver_application_delegate.h
@@ -27,8 +27,8 @@ class BrowserDriverApplicationDelegate : public mojo::ShellClient,
 
  private:
   // mojo::ShellClient:
-  void Initialize(mojo::Connector* connector, const std::string& url,
-                  const std::string& user_id, uint32_t id) override;
+  void Initialize(mojo::Connector* connector, const mojo::Identity& identity,
+                  uint32_t id) override;
   bool AcceptConnection(mojo::Connection* connection) override;
 
   // mus::mojom::AcceleratorHandler: