Here's the code:
name = makeName(6);
Since 'name' is undeclared, and window.name defaults to the DOM frame name API, this test spends a bunch of time getting and setting the name of the frame in the DOM.
Of course we want the DOM to be fast, but testing the DOM seems contrary to the goals of SunSpider.
This is fixed in a r-'ed patch attached to bug 17634, although with a slightly different rationale.
It looks like Maciej planned to fix this, but never got around to it.
I think the important issue is to pick a name that doesn't conflict with a DOM API. Whether the variable is declared as a var or not is no big deal.
Created attachment 99560 [details]
Committed r90318: <http://trac.webkit.org/changeset/90318>