XSSAuditor: treat questionmark as a non-canonical character.

LayoutTests/http/tests/security/xssAuditor/resources/echo-intertag.pl

Index: LayoutTests/http/tests/security/xssAuditor/resources/echo-intertag.pl
diff --git a/LayoutTests/http/tests/security/xssAuditor/resources/echo-intertag.pl b/LayoutTests/http/tests/security/xssAuditor/resources/echo-intertag.pl
index b2407deb4e4f6ed6bc9f8ad138f64aa8b3011a81..b790d513878ad393e9b2ce3026ba97b59d7f5b7f 100755
--- a/LayoutTests/http/tests/security/xssAuditor/resources/echo-intertag.pl
+++ b/LayoutTests/http/tests/security/xssAuditor/resources/echo-intertag.pl
@@ -92,7 +92,11 @@ if ($cgi->param('inHead')) {
 if ($cgi->param('replaceState')) {
     print "<script>history.replaceState({}, '', '#must-not-appear');</script>\n";
 }
-print $cgi->param('q'); # XSS reflected here.
+my $reflection = $cgi->param('q');
+my $pattern = "\xfe";
+my $replacement = "?";
+$reflection =~ s/$pattern/$replacement/g;  # pretend server translates high character 0xfe into literal "?".
+print $reflection; # XSS reflected here.
 if ($cgi->param('script-expression-follows')) {
     print "\n <script>42;</script>\n";
 }