UserAgent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_12_6) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/64.0.3282.186 Safari/537.36

Steps to reproduce the problem:

"Inspect element" doesn't work for elements within an iframe loaded via an extension page.

Example extension is attached.

I believe this is linked to OOPIF. Parent bug for OOPIF DevTools work:
https://bugs.chromium.org/p/chromium/issues/detail?id=652783

Example extension
=============

1. Drop all the attached files into a folder, and load the folder as an extension.
2. Click the extension "M" button top right. This will open an extension page with an iframe for https://chrome-bugs.neocities.org/select-element.html
3. Open 'Developer Tools'
4. Click 'Select an element in the page to inspect it'
5. Try selecting an element in the iframe-loaded page - you can't.

In contrast, selecting the element works just fine if you load https://chrome-bugs.neocities.org/select-element.html as a top level tab.

What is the expected behavior?
I can select an element on the iframe-loaded page.

What went wrong?
I can't select an element on the iframe-loaded page.

Did this work before? Yes 54.0.2840.71 (may work for later)

Chrome version: 64.0.3282.186  Channel: stable
OS Version: OS X 10.12.6
Flash Version:
 

Deleted: background.js 165 bytes

background.js 165 bytes View Download

Deleted: iframe.html 165 bytes

iframe.html 165 bytes View Download

Deleted: iframe.js 307 bytes

iframe.js 307 bytes View Download

Deleted: manifest.json 248 bytes

manifest.json 248 bytes View Download