Cascade shutdown of instances

mojo/shell/tests/lifecycle/lifecycle_unittest.mojom

Index: mojo/shell/tests/lifecycle/lifecycle_unittest.mojom
diff --git a/mojo/shell/tests/lifecycle/lifecycle_unittest.mojom b/mojo/shell/tests/lifecycle/lifecycle_unittest.mojom
index 1ae54e8eb3918a58e2747c10df79d265f091c56a..2197e3bcab3f61c0bb68815a05e026fd1758eddf 100644
--- a/mojo/shell/tests/lifecycle/lifecycle_unittest.mojom
+++ b/mojo/shell/tests/lifecycle/lifecycle_unittest.mojom
@@ -21,3 +21,12 @@ interface LifecycleControl {
   // longer tracking this application.
   CloseShellConnection();
 };
+
+// Implemented by an app that connects to another app, thereby creating an
+// instance for it in the shell.
+interface Parent {
+  // Connects to another app and runs the callback when that app has acked a
+  // Ping.
+  ConnectToChild() => ();
+  Quit();
+};