Merge from vscode 64980ea1f3f532c82bb6c28d27bba9ef2c5b4463 (#7206)

* Merge from vscode 64980ea1f3f532c82bb6c28d27bba9ef2c5b4463

* fix config changes

* fix strictnull checks

extensions/image-preview/src/dispose.ts

@@ -0,0 +1,42 @@
+/*---------------------------------------------------------------------------------------------
+ *  Copyright (c) Microsoft Corporation. All rights reserved.
+ *  Licensed under the Source EULA. See License.txt in the project root for license information.
+ *--------------------------------------------------------------------------------------------*/
+
+import * as vscode from 'vscode';
+
+export function disposeAll(disposables: vscode.Disposable[]) {
+	while (disposables.length) {
+		const item = disposables.pop();
+		if (item) {
+			item.dispose();
+		}
+	}
+}
+
+export abstract class Disposable {
+	private _isDisposed = false;
+
+	protected _disposables: vscode.Disposable[] = [];
+
+	public dispose(): any {
+		if (this._isDisposed) {
+			return;
+		}
+		this._isDisposed = true;
+		disposeAll(this._disposables);
+	}
+
+	protected _register<T extends vscode.Disposable>(value: T): T {
+		if (this._isDisposed) {
+			value.dispose();
+		} else {
+			this._disposables.push(value);
+		}
+		return value;
+	}
+
+	protected get isDisposed() {
+		return this._isDisposed;
+	}
+}