https://addons.mozilla.org/en-US/firefox/addon/chrome-mask/
From their about:
A little Firefox Extension that provides a one-click toggle to spoof as Chrome in Firefox - or, in other words, to put on the Chrome Mask.
There are a lot of generic "User Agent spoof" extensions. However, this extension does a few things differently:
- Instead of overriding the User Agent string on all sites, this extension allows you to only look like Chrome on specific sites.
- Unlike some extensions with outdated version numbers and UA strings, this extension automatically updates the Chrome version it pretends to be. It does that by querying a simple API every 24 hours.
- You don't have to pick the correct Operating System manually; this extension does it for you.
- This extension also shims a few additional JavaScript attributes, like navigator.vendor or the global chrome object, to pass common browser checks.