Move 'id'-related invalidation to SVGElement::attributeChanged

There's no reason for 'id'-related invalidation to reside in
SVGElement::svgAttributeChanged since it has no interaction with an
(animated) SVG DOM attribute. Move it to SVGElement::attributeChanged
instead.
This will also enable us to make use of the old/new value that is
available in attributeChanged().

BUG=454767

Review-Url: https://codereview.chromium.org/2645383002
Cr-Commit-Position: refs/heads/master@{#445393}
1 file changed