Re: [css3-conditional] navigator.supportsCSS rather than window.supportsCSS

|  I don't think adding on to window is a big deal.  If we do want to
|  avoid doing it, though, I suggest defining a new top-level interface
|  named "CSS" and hanging it off of that.  It's short and topical, and
|  it would be convenient for hanging some of the new css value
|  constructors we'll want for the cssom values api.

I'm afraid WebIDL doesn't support nested interfaces or namespaces right now.

##  For every interface that [should be available to JS] a
##  corresponding property MUST exist on the ECMAScript
##  global object. The name of the property is the identifier of
##  the interface, and its value is an object called the interface
##  object.

BTW, CSSStyleDeclaration isn't that long to type.

Plus, remember, your IDE supports intellisense ^_^