Gracefully handle mixed content checking on detached resource fetches.

LayoutTests/fast/xmlhttprequest/xmlhttprequest-detached-mixedcontent-no-crash.html

Index: LayoutTests/fast/xmlhttprequest/xmlhttprequest-detached-mixedcontent-no-crash.html
diff --git a/LayoutTests/fast/files/file-reader-detached-no-crash.html b/LayoutTests/fast/xmlhttprequest/xmlhttprequest-detached-mixedcontent-no-crash.html
similarity index 68%
copy from LayoutTests/fast/files/file-reader-detached-no-crash.html
copy to LayoutTests/fast/xmlhttprequest/xmlhttprequest-detached-mixedcontent-no-crash.html
index e38052a4eb1d22d19a9a86b1926b11828a9bbb86..0bcd6c8cf56ebce87918b703f81c4a1b3effc25b 100644
--- a/LayoutTests/fast/files/file-reader-detached-no-crash.html
+++ b/LayoutTests/fast/xmlhttprequest/xmlhttprequest-detached-mixedcontent-no-crash.html
@@ -4,18 +4,19 @@
 <script src="../../resources/js-test.js"></script>
 </head>
 <script>
-description("Accessing FileReader when in a detached state.");
+description("Performing mixed content checks in a detached setting shouldn't crash.");
 
 window.jsTestIsAsync = true;
 
 var w;
-var fileReader;
+var xhr;
 function processMessage(event) {
     if (event.data == "opened") {
-        fileReader = new w.FileReader();
+        xhr = new w.XMLHttpRequest();
+        xhr.open('GET', 'http://user:pass@127.0.0.1:8000/doesNotExist', false);
         w.close();
     } else if (event.data == "closed") {
-        shouldThrow("fileReader.readAsArrayBuffer(new File(['hello'], 'world.html'))");
+        shouldThrow("xhr.send()");
         finishJSTest();
     }
 }