set focus on iframe window and on webview, fixes #5070

src/vs/workbench/parts/html/browser/webview.html

@@ -34,7 +34,7 @@
 
 		// propagate focus
 		ipcRenderer.on('focus', function() {
-			target.contentDocument.body.focus();
+			target.contentWindow.focus();
 		});
 
 		// update iframe-contents

src/vs/workbench/parts/html/browser/webview.ts

@@ -110,6 +110,7 @@ export default class Webview {
 	}
 
 	focus(): void {
+		this._webview.focus();
 		this._send('focus');
 	}