[webauthn] Should the "authentication" attribute on Navigator be [SameObject]?

bzbarsky has just created a new issue for 
https://github.com/w3c/webauthn:

== Should the "authentication" attribute on Navigator be [SameObject]?
 ==
And in general, should it have some sort of processing model defined?
  Right now nothing defines what this attribute actually returns.  
Does the returned value depend on the "this" value, or on the Realm of
 the attribute getter, or something else?

Presumably this should be [SameObject] hence and the return value 
should depend only on the "this" value, and should be associated to 
the same global as the "this" value.

Please view or discuss this issue at 
https://github.com/w3c/webauthn/issues/249 using your GitHub account