[XHR] Tidy up files for testing XHR's error for mixed content check failure

LayoutTests/http/tests/security/mixedContent/resources/frame-with-insecure-async-xhr-post.html

Index: LayoutTests/http/tests/security/mixedContent/resources/frame-with-insecure-async-xhr-post.html
diff --git a/LayoutTests/http/tests/security/mixedContent/resources/frame-with-insecure-async-xhr-post.html b/LayoutTests/http/tests/security/mixedContent/resources/frame-with-insecure-async-xhr-post.html
new file mode 100644
index 0000000000000000000000000000000000000000..d618e4312cb9b1489c255b7b0fe4d6f33da1d507
--- /dev/null
+++ b/LayoutTests/http/tests/security/mixedContent/resources/frame-with-insecure-async-xhr-post.html
@@ -0,0 +1,9 @@
+<script>
+var xhr = new XMLHttpRequest();
+xhr.onerror = function()
+{
+    window.opener.postMessage('done', '*');

[Mike West, 2015/07/27 09:09:32]

Can you add a success handler which postMessages something other than "done",
and verify the result in the parent page? As-is, this test will timeout if we
break things; I'd rather be explicit about failure.

[tyoshino (SeeGerritForStatus), 2015/07/27 09:20:01]

Added!

+};
+xhr.open("POST", "http://127.0.0.1:8000/xmlhttprequest/resources/access-control-allow-lists.php?origin=*", true);
+xhr.send("foo");
+</script>