Allows top level non-XUL documents to share this code. Three tests had to
be adjusted to account for the attributes being chrome only now and not
available to content privilege XUL. In two tests, the values attributes
are now simply undefined. The crashtest was converted to a chrome
mochitest to preserve what it was testing.
MozReview-Commit-ID: 99w9Ax4et3C
--HG--
rename : dom/base/crashtests/473284.xul => dom/base/test/chrome/test_bug473284.xul
extra : rebase_source : 924d34a88fe8a48d766f78b02e64275f6e7cdc2b
