GODT-2039: bridge monitors bridge-gui via its PID.

internal/app/base/base.go

@@ -76,6 +76,7 @@ const (
 	flagRestart         = "restart"
 	FlagLauncher        = "launcher"
 	FlagNoWindow        = "no-window"
+	FlagParentPID       = "parent-pid"
 )
 
 type Base struct {
@@ -324,6 +325,12 @@ func (b *Base) NewApp(mainLoop func(*Base, *cli.Context) error) *cli.App {
 			Usage:  "The launcher to use to restart the application",
 			Hidden: true,
 		},
+		&cli.IntFlag{
+			Name:   FlagParentPID,
+			Usage:  "The PID of the process that started the application. Ignored if frontend is not gRPC",
+			Hidden: true,
+			Value:  -1,
+		},
 	}
 
 	return app