Removing the SVG instance tree (SVG2 issue 51)

www-svg,

Can we remove the instance tree in SVG2?

Over the holidays I implemented SVG's <use> in terms of pure web
components. This works well and <use>+web components will vastly simplify
the SVG2 spec. Unfortunately, the instance tree is incompatible with shadow
dom and I'd like to propose removing the instance tree.

For users, the instance tree has not been popular. I added a counter to
Chrome's usage statistics in http://crbug.com/313438 and found zero users
of instanceRoot. I searched all of github and found only 9
non-layouttest<https://github.com/search?l=javascript&p=1&q=correspondingElement&ref=cmdform&type=Code>uses
of correspondingElement.

For implementors, the instance tree is slow and riddled with tricky
security concerns (we call it the <use-after-free> element in Chrome). It
does not look like Gecko will implement the instance tree (
https://bugzilla.mozilla.org/show_bug.cgi?id=508561).

Can we unify on the event model used by shadow dom and drop the instance
tree?
http://www.w3.org/TR/components-intro/#events

Philip