Merge from master

src/vs/base/worker/defaultWorkerFactory.ts

@@ -2,10 +2,9 @@
  *  Copyright (c) Microsoft Corporation. All rights reserved.
  *  Licensed under the Source EULA. See License.txt in the project root for license information.
  *--------------------------------------------------------------------------------------------*/
-'use strict';
 
 import { globals } from 'vs/base/common/platform';
-import { logOnceWebWorkerWarning, IWorker, IWorkerCallback, IWorkerFactory } from 'vs/base/common/worker/simpleWorker';
+import { IWorker, IWorkerCallback, IWorkerFactory, logOnceWebWorkerWarning } from 'vs/base/common/worker/simpleWorker';
 
 function getWorker(workerId: string, label: string): Worker {
 	// Option for hosts to overwrite the worker script (used in the standalone editor)
@@ -32,7 +31,7 @@ function getWorker(workerId: string, label: string): Worker {
 class WebWorker implements IWorker {
 
 	private id: number;
-	private worker: Worker;
+	private worker: Worker | null;
 
 	constructor(moduleId: string, id: number, label: string, onMessageCallback: IWorkerCallback, onErrorCallback: (err: any) => void) {
 		this.id = id;
@@ -57,7 +56,9 @@ class WebWorker implements IWorker {
 	}
 
 	public dispose(): void {
-		this.worker.terminate();
+		if (this.worker) {
+			this.worker.terminate();
+		}
 		this.worker = null;
 	}
 }
@@ -66,10 +67,10 @@ export class DefaultWorkerFactory implements IWorkerFactory {
 
 	private static LAST_WORKER_ID = 0;
 
-	private _label: string;
+	private _label: string | undefined;
 	private _webWorkerFailedBeforeError: any;
 
-	constructor(label: string) {
+	constructor(label: string | undefined) {
 		this._label = label;
 		this._webWorkerFailedBeforeError = false;
 	}