Fix webviews for electron 7

Caused by #83796

Also re-enables the webview tests

extensions/vscode-api-tests/src/singlefolder-tests/webview.test.ts

@@ -13,7 +13,7 @@ const webviewId = 'myWebview';
 
 const testDocument = join(vscode.workspace.rootPath || '', './bower.json');
 
-suite.skip('Webview tests', () => {
+suite('Webview tests', () => {
 	const disposables: vscode.Disposable[] = [];
 
 	function _register<T extends vscode.Disposable>(disposable: T) {

src/vs/code/electron-main/app.ts

@@ -191,7 +191,8 @@ export class CodeApplication extends Disposable {
 				webPreferences.nodeIntegration = false;
 
 				// Verify URLs being loaded
-				if (isValidWebviewSource(params.src) && isValidWebviewSource(webPreferences.preload)) {
+				// https://github.com/electron/electron/issues/21553
+				if (isValidWebviewSource(params.src) && isValidWebviewSource((webPreferences as { preloadURL: string }).preloadURL)) {
 					return;
 				}