XSSAuditor: Don't rely on implicit casting when copying the document's KURL to String.
https://bugs.webkit.org/show_bug.cgi?id=110859

Reviewed by Jochen Eisinger.

XSSAuditor::init should explicitly make a thread-safe copy of the
document's URL as a String rather than relying on implicit casting from
a copy of the KURL.

This shouldn't change any visible behavior; all existing XSSAuditor
tests should continue to pass. They'll now just be a bit more smug while
doing so.

* html/parser/XSSAuditor.cpp:
(WebCore::XSSAuditor::init):


git-svn-id: http://svn.webkit.org/repository/webkit/trunk@144036 268f45cc-cd09-0410-ab3c-d52691b4dbfc