UserAgent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_11_6) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/57.0.2987.110 Safari/537.36

Steps to reproduce the problem:
1. Go to https://developer.chrome.com/extensions/manifest/sandbox
2. Documentation instructs developers to use a "webview" - which is not allowed in a Chrome Extension.
3. Developer cries.

What is the expected behavior?
Either restore the ability for Extensions to have sandboxed iframes loading external content, or add webview supports to Extensions.

What went wrong?
As of Chrome version 57, Chrome will no longer allow external web content (including embedded frames and scripts) inside sandboxed pages. The documentation suggests that developers "Please use a webview instead." But webviews are not allowed in a Chrome Extension.

Did this work before? N/A 

Chrome version: 57.0.2987.110  Channel: stable
OS Version: OS X 10.11.6
Flash Version: Shockwave Flash 25.0 r0

This change was released with little to no advance communication and has completely broken my Chrome extension, causing a crisis for my business.