UserAgent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/55.0.2868.3 Safari/537.36

Steps to reproduce the problem:
1. enable MD settings via #enable-md-settings flag;
2. navigate to one sub setting of site settings like
chrome://settings/siteSettings/notifications
3. add an extension url to exception like
chrome-extension://efhgfbfpcbnnbicfphagcjmgjfjmojfd/
4. reload

What is the expected behavior?
the added site appears in site list and exception rule works.

What went wrong?
1. the Block/Allow section which the site is added to disappears with errors in console, see the attached screenshot for details (shot on a canary build which also got this problem).
2. the rule doesn't work.

Did this work before? N/A 

Chrome version: 55.0.2868.3  Channel: dev
OS Version: 10.0
Flash Version: Shockwave Flash 23.0 r0

i found this problem because i want to use notification in an extension background page but notification permission request popup wouldn't show up (reasonable for background page? hmm...) and i had to manually add it to site exceptions.
In traditional settings UI that works fine and previously added sites show up in MD settings list -- but adding site in MD settings doesn't work.
And now i can switch back to traditional UI, add site, switch to MD settings and rules work well -- but this requires restarting chrome twice.
 

Deleted: extension_url_breaks_md_settings.png 123 KB

	extension_url_breaks_md_settings.png 123 KB View Download