Remove several uses of toWebCoreStringWithNullCheck(v8::Handle<v8::Value>)

LayoutTests/fast/xmlhttprequest/xmlhttprequest-open-exceptions.html

Index: LayoutTests/fast/xmlhttprequest/xmlhttprequest-open-exceptions.html
diff --git a/LayoutTests/fast/xmlhttprequest/xmlhttprequest-open-exceptions.html b/LayoutTests/fast/xmlhttprequest/xmlhttprequest-open-exceptions.html
index 6a869cdc2d1d994835a2a286e92c79b73d017485..2e767cb19fa1c89e15c1c9440a7eb5a4e96f6de9 100644
--- a/LayoutTests/fast/xmlhttprequest/xmlhttprequest-open-exceptions.html
+++ b/LayoutTests/fast/xmlhttprequest/xmlhttprequest-open-exceptions.html
@@ -26,6 +26,14 @@
             xhrException = e;
             shouldBeEqualToString("xhrException.message", "Refused to connect to 'http://not.example.com/' because it violates the document's Content Security Policy.");
         }
+
+        var badString = { toString: function() { throw "Exception in toString()"; } };
+        var xhr = new XMLHttpRequest();
+        shouldBe("xhr.readyState", "XMLHttpRequest.UNSENT");
+        shouldThrow("xhr.open('GET', 'resources/xmlhttprequest-get-data.xml', true, badString, 'password');", "'Exception in toString()'");
+        shouldBe("xhr.readyState", "XMLHttpRequest.UNSENT");
+        shouldThrow("xhr.open('GET', 'resources/xmlhttprequest-get-data.xml', true, 'username', badString);", "'Exception in toString()'");
+        shouldBe("xhr.readyState", "XMLHttpRequest.UNSENT");
     </script>
 </body>
 </html>