This removes the (default disabled) node.rootNode readonly attribute
and replaces it with a node.getRootNode() function per WhatWG
spec discussion.
Based on work by John Dai <jdai@mozilla.com>
With the big amount of code churn around DOM a lot of tests
broke severely enough that they caused build bustage.
This commit cleans up, removes or otherwise fixes tests
that are broken, no longer relevant or obsolete.
We call attributeChangedCallback in two cases:
1. When any of the attributes in the observed attribute list has changed, appended, removed, or replaced.
2. When upgrading an element, for each attribute in element's attribute list that is in the observed attribute list.
Note: w/ Fixup for not implementing an API Enhancement Bug 1363481.
Tag UXP Issue #1344
