Add "allow" attribute (feature-policy)

[MaiklT]

Description

A feature policy enables and disables certain web platform features on the web site and those that are embedded. The attribute "allow" in the iframe tag may override this policy.

Example:

feature-policy: vibrate 'self';
...
<iframe src="https://somewhere.else" allow="vibrate">

Solution

A module setting to define the "allow" value.

[MaiklT]

There are more possible attributes, e.g. "sandbox". Maybe it is better to create a possibility to add attributes that works in the same way as the "Parameters" tab.

[noahbast]

We need this feature as well:
https://dev.chromium.org/Home/chromium-security/deprecating-permissions-in-cross-origin-iframes

For now, I'm going to have to put the iframe in an HTML module.

[MaiklT]

@noahbast Thanks for your inquirement. I have nearly forgotten this issue... ;-)

I will soon start working on this.