Giving focus to an app shim brings windows belonging to that app to the foreground.

apps/app_shim/app_shim_host_mac.h

Index: apps/app_shim/app_shim_host_mac.h
diff --git a/apps/app_shim/app_shim_host_mac.h b/apps/app_shim/app_shim_host_mac.h
index 8ebc0cd179cd8d15c81df21b20941b8c1e8b1211..fbfd0fa2573d7899fbe6bddec661dbe49bca348b 100644
--- a/apps/app_shim/app_shim_host_mac.h
+++ b/apps/app_shim/app_shim_host_mac.h
@@ -60,6 +60,11 @@ class AppShimHost : public IPC::Listener,
   // app shim to send multiple launch messages.
   void OnLaunchApp(std::string profile, std::string app_id);
 
+  // Called when the app shim process notifies that the app should be brought
+  // to the front (i.e. the user has clicked on the app's icon in the dock or
+  // Cmd+Tabbed to it.)
+  void OnFocus();
+
   bool LaunchAppImpl(const std::string& profile_dir, const std::string& app_id);
 
   // The AppShimHost listens to the NOTIFICATION_EXTENSION_HOST_DESTROYED