Comment 4 for bug 1628956

Motivation for this new requirement is:

## Why

 Each particular network your computer and browser run in has its own set of
 network conditions, routers, proxies and MITM situations.

 Changing between networks also changes proxies. Intercepting or explicit,
 willing or unwilling, HTTP or even HTTPS with custom installed trust-roots.
 This makes the web content cache, the cookie store and others to save
 contents from one network that is potentially different than what is received
 over other networks. It can lead to content pollution and information leaks,
 on purpose by malicious actors or just by mistake.

see the details here https://bug1240932.bmoattachments.org/attachment.cgi?id=8709691