UserAgent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_12_0) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/55.0.2867.0 Safari/537.36

Steps to reproduce the problem:
1. Open a version of Chrome which supports Custom Elements V1 and Shadow DOM 
2. Ensure that you have an autofill profile set with first name, last name and email address.
2. Open the codepen URL linked below

3. Click in the first input in the "Form with native inputs" section
3a. Hover over the first name shown in the autofill dropdown
3b. Notice that other fields in the group receive autofill values

4. Click in the first input in the "Form with inputs generated" section
4a. Hover over the first name shown in the autofill dropdown
4b. Notice that other fields in the group *do not* receive autofill values

http://s.codepen.io/bgummeratlassian/debug/Egkarq

What is the expected behavior?
Inputs generated inside shadow roots should be autofilled, similar to the autofill behaviour shown with native inputs.

What went wrong?
The inputs in the "Form with inputs generated" section did not autofill as expected.

This means that there is currently no way to generate input elements inside a shadow root while retaining support for autofill. The workaround is to require custom element consumers to provide light DOM inputs.

Did this work before? Yes With native form inputs

Chrome version: 55.0.2867.0  Channel: canary
OS Version: OS X 10.12.0
Flash Version: Shockwave Flash 23.0 r0

It's not 100% clear from my research if this is a bug. It may be intended behaviour associated with shadow root encapsulation, or may be a bug.

Regardless of how this ticket is classified, I think there needs to be a way to autofill related custom elements which each generate form elements inside their shadow roots.

https://github.com/w3c/webcomponents/issues/187 is somewhat related to this.