UserAgent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_12_2) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/56.0.2924.87 Safari/537.36

Steps to reproduce the problem:
1. Create a web page that loads a child frame. The child frame contains 1 text input with 'autofocus' attribute set
2. In the parent web page should contain a script that defines the creation of an iframe element with the src attribute "chrome-extension://<your extension id>/<some web accessbile file>.html.  Use document.body.appendChild(new_frame_element) to add the created frame to the DOM
3. Load the parent web page in the browser.

This flow is fully demo'd in an example project:

1. Install the test extension from https://github.com/Fillr/chrome-ext-iframe-blur
2. run the server (./run/server from project root)
3. Observe the console after loading http://localhost:6969/top.html

What is the expected behavior?
The field in the subframe with autofocus should remain focussed. 
No blur event should be raised at all

What went wrong?
It feels like any url loaded in to the parent frame over chrome-extension scheme triggers a blur on child frames.  The demo project shows that urls loaded over http/https do not trigger the same blur behaviour.

Did this work before? N/A 

Does this work in other browsers? Yes

Chrome version: 56.0.2924.87  Channel: stable
OS Version: OS X 10.12.2
Flash Version: 

Please refer to the readme at https://github.com/Fillr/chrome-ext-iframe-blur for a full test case and steps to reproduce