Web Inspector: Properly handle the rule addition to an XML or SVG document.
https://bugs.webkit.org/show_bug.cgi?id=113185

Reviewed by Pavel Feldman.

* inspector/InspectorCSSAgent.cpp:
(WebCore::InspectorCSSAgent::viaInspectorStyleSheet):

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@146760 268f45cc-cd09-0410-ab3c-d52691b4dbfc