src/vs/workbench/services/lifecycle/browser/lifecycleService.ts/BrowserLifecycleService/onBeforeUnload
class BrowserLifecycleService:	private onBeforeUnload(event: BeforeUnloadEvent): void {

		// Before unload ignored (once)
		if (this.ignoreBeforeUnload) {
			this.logService.info('[lifecycle] onBeforeUnload triggered but ignored once');

			this.ignoreBeforeUnload = false;
		}

		// Before unload with veto support
		else {
			this.logService.info('[lifecycle] onBeforeUnload triggered and handled with veto support');

			this.doShutdown(() => this.vetoBeforeUnload(event));
		}
	}