UserAgent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_12_0) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/56.0.2888.0 Safari/537.36

Steps to reproduce the problem:
console.log(message) calls made from within an iframe loaded on an extension page have stopped working. It's now borked for console.log calls made in the iframe page itself, an extension content script, or a script injected by the content script.

Example extension is attached, and bisect is below.

The bisect suggests that this regression is related to "Enable Site Isolation for Extensions" being switched on. This is hampering efforts of external developers such as myself to submit bugs for this new feature, as it's not possible to "sys-out debug". That's what I was trying to do when I ran into this problem.

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 http://chrome-bugs.neocities.org/console.html
3. Open the console on the extension page, and look for 3 console.log messages.

When working, the console will show:

console.html:17 Message from page: http://chrome-bugs.neocities.org/console.html
contentscript.js:1 Message from content script: http://chrome-bugs.neocities.org/console.html
(unknown) Message from script injected by content script: http://chrome-bugs.neocities.org/console.html

When not working, the console shows no messages.

Bisect
====

https://omahaproxy.appspot.com
53.0.2785.14 (works) => 403382
56.0.2888.0  (busted) => 424625

export EXT_DIR=location-of-extension-folder
python bisect-builds.py -a mac -g 403382 -b 424625 --use-local-cache -- --load-extension=${EXT_DIR}

You are probably looking for a change made after 414868 (known good), but no later than 414880 (first known bad).
CHANGELOG URL:
  https://chromium.googlesource.com/chromium/src/+log/6873421b480c8b2716590147e17d2036734304e5..9738e8297d39ff71bc772514066b5d7eadd4c4da

Suspicious:
"Enable Site Isolation for Extensions."
https://chromium.googlesource.com/chromium/src/+/d8f0aefde00132b06bd97cb17555f2ec89a0c203

What is the expected behavior?
console.log(message) calls made from within an iframe loaded on an extension page should work.

What went wrong?
console.log(message) calls made from within an iframe loaded on an extension page have stopped working.

Did this work before? Yes 53.0.2785.14

Chrome version: 56.0.2888.0  Channel: canary
OS Version: OS X 10.12.0
Flash Version: Shockwave Flash 23.0 r0
 

Deleted: manifest.json 483 bytes

manifest.json 483 bytes View Download

Deleted: iframe.js 273 bytes

iframe.js 273 bytes View Download

Deleted: iframe.html 165 bytes

iframe.html 165 bytes View Download

Deleted: contentscript.js 311 bytes

contentscript.js 311 bytes View Download

Deleted: background.js 213 bytes

background.js 213 bytes View Download