Node::attach() should be after attaching children in Element::attach().

Node::attach() should be after attaching children in Element::attach().
https://bugs.webkit.org/show_bug.cgi?id=79201

Reviewed by Hajime Morita.

In Element::attach(), Node::attach() is called before attaching children if a shaodw root exists.
This may cause O(N^2) problem in NodeRenderingContext.

No new tests. Existing tests should cover this.

* dom/Element.cpp:
(WebCore::Element::attach):

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@108470 268f45cc-cd09-0410-ab3c-d52691b4dbfc