Redirect POST requests using .py resource

Part of #11269.

Also see #11343.

html/browsers/history/the-location-interface/reload_post_1.html → html/browsers/history/the-location-interface/reload_post_1-manual.html

@@ -4,7 +4,7 @@
 <script src="/resources/testharnessreport.js"></script>
 <div id="log"></div>
 <script>
-var win = window.open("reload_post_1-1.html");
+var win = window.open("resources/reload_post_1-1.py");
 var t = async_test();
 var posted = false;
 var reloaded = false;

html/browsers/history/the-location-interface/resources/reload_post_1-1.py

@@ -0,0 +1,13 @@
+def main(request, response):
+    headers = [("Content-Type", "text/html")]
+    return headers, '''
+        <script>
+            onload = function() {opener.next()}
+            document.write(Math.random());
+        </script>
+        <form method="POST" action="">
+            <input type=hidden name=test value=test>
+            <input type=submit>
+        </form>
+        <button onclick="location.reload()">Reload</button>
+    '''