diff --git a/tests/resources/testharness.js b/tests/resources/testharness.js
--- a/tests/resources/testharness.js
+++ b/tests/resources/testharness.js
@@ -1341,39 +1341,41 @@ policies and contribution forms [3].
                                      style_element.innerHTML = "table#results > tbody > tr."+result_class+"{display:none}";
                                      output_document.body.appendChild(style_element);
                                  } else if (style_element && input_element.checked) {
                                      style_element.parentNode.removeChild(style_element);
                                  }
                              });
                 });

-        var template = ["section", {},
-                        ["h2", {}, "Details"],
-                        ["table", {"id":"results"},
-                        ["tr", {},
-                         ["th", {}, "Result"],
-                         ["th", {}, "Test Name"],
-                         ["th", {}, "Message"]
-                        ],
-                        ["tbody", {},
-                        function(vars) {
-                            var rv = map(vars.tests, function(test) {
-                                             var status = status_text[test.status];
-                                             return  ["tr", {"class":status_class(status)},
-                                                      ["td", {}, status],
-                                                      ["td", {}, test.name],
-                                                      ["td", {}, test.message ? test.message : " "]
-                                                     ];
-                                         });
-                            return rv;
-                        }]
-                       ]];
+        var section = document.createElement("section");
+        log.appendChild(section);
+        // The table might have tens of thousands of rows.  Build it using
+        // string concatenation and append all at once for performance's sake.
+        var html = "<h2>Details</h2><table id=results><tr><th>Result<th>Test Name<th>Message<tbody>";

-        log.appendChild(render(template, {tests:tests}, output_document));
+        var escape_html = function(input) {
+                // Warning: only use in attributes if they're double-quoted.
+                return input
+                    .replace(/\&/g, "&amp;")
+                    .replace(/</g, "&lt;")
+                    .replace(/"/g, "&quot;");
+            };
+
+        for (var i = 0; i < tests.length; i++)
+        {
+            html += '<tr class="'
+                + escape_html(status_class(status_text[tests[i].status]))
+                + '">'
+                + '<td>' + escape_html(status_text[tests[i].status])
+                + '<td>' + escape_html(tests[i].name)
+                + '<td>' + escape_html(tests[i].message ? tests[i].message : " ");
+        }
+
+        section.innerHTML = html;
     };

     var output = new Output();
     add_start_callback(function (properties) {output.setup(properties);});
     add_result_callback(function (test) {output.show_status(tests);});
     add_completion_callback(function (tests, harness_status) {output.show_results(tests, harness_status);});

     /*