Merge from vscode 8e0f348413f4f616c23a88ae30030efa85811973 (#6381)

* Merge from vscode 8e0f348413f4f616c23a88ae30030efa85811973

* disable strict null check

src/vs/platform/lifecycle/browser/lifecycleService.ts

@@ -0,0 +1,59 @@
+/*---------------------------------------------------------------------------------------------
+ *  Copyright (c) Microsoft Corporation. All rights reserved.
+ *  Licensed under the Source EULA. See License.txt in the project root for license information.
+ *--------------------------------------------------------------------------------------------*/
+
+import { ShutdownReason, ILifecycleService } from 'vs/platform/lifecycle/common/lifecycle';
+import { ILogService } from 'vs/platform/log/common/log';
+import { AbstractLifecycleService } from 'vs/platform/lifecycle/common/lifecycleService';
+import { localize } from 'vs/nls';
+import { ServiceIdentifier } from 'vs/platform/instantiation/common/instantiation';
+
+export class BrowserLifecycleService extends AbstractLifecycleService {
+
+	_serviceBrand: ServiceIdentifier<ILifecycleService>;
+
+	constructor(
+		@ILogService readonly logService: ILogService
+	) {
+		super(logService);
+
+		this.registerListeners();
+	}
+
+	private registerListeners(): void {
+		window.onbeforeunload = () => this.beforeUnload();
+	}
+
+	private beforeUnload(): string | null {
+		let veto = false;
+
+		// Before Shutdown
+		this._onBeforeShutdown.fire({
+			veto(value) {
+				if (value === true) {
+					veto = true;
+				} else if (value instanceof Promise && !veto) {
+					console.warn(new Error('Long running onBeforeShutdown currently not supported'));
+					veto = true;
+				}
+			},
+			reason: ShutdownReason.QUIT
+		});
+
+		// Veto: signal back to browser by returning a non-falsify return value
+		if (veto) {
+			return localize('lifecycleVeto', "Changes that you made may not be saved. Please check press 'Cancel' and try again.");
+		}
+
+		// No Veto: continue with Will Shutdown
+		this._onWillShutdown.fire({
+			join() {
+				console.warn(new Error('Long running onWillShutdown currently not supported'));
+			},
+			reason: ShutdownReason.QUIT
+		});
+
+		return null;
+	}
+}