[nickpsecurity]

They probably should've linked to a better intro to Secure Contexts than a standards document. Here's a simple explanation for them from Mozilla:

https://developer.mozilla.org/en-US/docs/Web/Security/Secure...

Features Restricted to Secure Contexts:

https://developer.mozilla.org/en-US/docs/Web/Security/Secure...

Chrome's Secure Origins seem to be the same thing:

https://www.chromium.org/Home/chromium-security/prefer-secur...

[annevk]

I adjusted the post to take your feedback into account. Thanks!