Load script async in markdown preview

extensions/markdown/media/main.js

@@ -145,7 +145,7 @@
 	var marker = new ActiveLineMarker();
 	const settings = JSON.parse(document.getElementById('vscode-markdown-preview-data').getAttribute('data-settings'));
 
-	window.addEventListener('load', () => {
+	function onLoad() {
 		if (settings.scrollPreviewWithEditorSelection) {
 			const initialLine = +settings.line;
 			if (!isNaN(initialLine)) {
@@ -155,7 +155,14 @@
 				}, 0);
 			}
 		}
-	});
+	}
+
+	if (document.readyState === 'loading') {
+		document.addEventListener('DOMContentLoaded', onLoad);
+	} else {
+		onLoad();
+	}
+
 
 	window.addEventListener('resize', () => {
 		scrollDisabled = true;

extensions/markdown/src/previewContentProvider.ts

@@ -196,7 +196,7 @@ export class MDDocumentContentProvider implements vscode.TextDocumentContentProv
 	private getScripts(nonce: string): string {
 		const scripts = [this.getMediaPath('main.js')].concat(this.extraScripts.map(resource => resource.toString()));
 		return scripts
-			.map(source => `<script src="${source}" nonce="${nonce}"></script>`)
+			.map(source => `<script async src="${source}" nonce="${nonce}"></script>`)
 			.join('\n');
 	}
 

src/vs/workbench/parts/html/browser/webview-pre.js

@@ -86,7 +86,7 @@
 		});
 	}
 
-	document.addEventListener("DOMContentLoaded", function (event) {
+	document.addEventListener('DOMContentLoaded', function (event) {
 		ipcRenderer.on('baseUrl', function (event, value) {
 			initData.baseUrl = value;
 		});