src/vs/workbench/services/lifecycle/browser/lifecycleService.ts/BrowserLifecycleService/vetoBeforeUnload
class BrowserLifecycleService:	private vetoBeforeUnload(event: BeforeUnloadEvent): void {
		event.preventDefault();
		event.returnValue = localize('lifecycleVeto', "Changes that you made may not be saved. Please check press 'Cancel' and try again.");
	}