As seen on https://phabricator.services.mozilla.com/D107645#inline-603500 the WebDriver:NewSession command returns a rotatable capability that is not part of the WebDriver specification. At least it would need a moz: prefix.

But given that there is no real usage of the capability it should basically get removed.

https://searchfox.org/mozilla-central/search?q=rotatable&path=

James, is that rotatable capability maybe part of some WebDriver extension that I'm not aware of? If not, shall we remove it, or add the moz: prefix? It mainly indicates that a device (e.g Android) can be rotated, and different screen orientations are available.

I would propose to remove it.

It appears to exist in Selenium: https://github.com/SeleniumHQ/selenium/blob/0f197cbd4fa9acdd2ac3ddebbe0cc9b4ca26bff8/java/client/src/org/openqa/selenium/remote/CapabilityType.java#L38 I'm not aware of any standard here and afaict we don't support setting the capability. So the chance of breaking someone is small but non-zero.

Oh right. So it's also here:

https://github.com/SeleniumHQ/selenium/blob/0f197cbd4fa9acdd2ac3ddebbe0cc9b4ca26bff8/javascript/webdriver/capabilities.js#L128-L129

David, what do you think should we do with this capability? Is that maybe a left-over from the old wire protocol?

It might be a hangover. The Java code will, by how it's designed, try cast to a rotatable and then fail if the browser can't do it. feel free to remove it.,

This capability is not part of the WebDriver specification
and might have used in the past for B2G to indicate that
a mobile device allows screen orientation changes. This is
no longer used.

https://hg.mozilla.org/mozilla-central/rev/5494e55dcb1b