XSSAuditor has a subtle race condition when used with the threaded HTML parser
https://bugs.webkit.org/show_bug.cgi?id=111253

Reviewed by Eric Seidel.

We were refing and derefing a StringImpl for a main-thread
AtomicString. Using QualifiedNames on the background thread is very
fragile and we should figure out a more robust solution.

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


git-svn-id: http://svn.webkit.org/repository/webkit/trunk@144549 268f45cc-cd09-0410-ab3c-d52691b4dbfc