Re: variable declarations shadowing named properties on window

Boris Zbarsky:
> What Gecko actually uses is more like this, I believe:
>
> Object.prototype <- [named props obj] <- Window.prototype <- window
>
> Note that this does not obviate the need for the no-overriding-builtins
> stuff, though, because you don't want to shadow Object.prototype on the
> named props object either...

Yeah.

> So it might be possible to move the named props object to the other spot
> in the proto chain.

Even though there's only one instance of Window that inherits from a 
given Window.prototype, it makes slightly more sense to me to have the 
instance-specific named properties object closer to the instance, before 
inheriting from Window.prototype.

I think we can just trigger this "add an extra object in the proto 
chain" based on [ReplaceableNamedProperties], so no changes to HTML's 
IDL would be needed.