Debugging HTML content provider in VSCode

VSCodeDevTools.txt

// Instructions to open Chrome DevTools on the HTML preview window:
//
// 1. With the HTML preview window open, click Help->Toggle Developer Tools.
//    Note that this DevTools is docked and is only for VSCode itself.
//
// 2. In the Console tab, paste this line:
//    document.body.querySelector('webview').getWebContents().openDevTools();
//
// 3. You now have a second DevTools, the new one is un-docked.  Close the
//    old docked one.
//
// 4. In the top of the Console tab of the remaining un-docked DevTools,
//    click the pull-down and change "top" to "_target (webview.html)".
//    Now you can debug the HTML preview in the sandboxed iframe.