Enable ServerTiming support

third_party/WebKit/LayoutTests/external/wpt/common/performance-timeline-utils.js

+var performanceNamespace = window.performance;
+var namespace_check = false;
+function wp_test(func, msg, properties)
+{
+  // only run the namespace check once
+  if (!namespace_check)
+  {
+    namespace_check = true;
+
+    if (performanceNamespace === undefined || performanceNamespace == null)
+    {
+      // show a single error that window.performance is undefined
+      test(function() { assert_true(performanceNamespace !== undefined && performanceNamespace != null, "window.performance is defined and not null"); }, "window.performance is defined and not null.", {author:"W3C http://www.w3.org/",help:"http://www.w3.org/TR/navigation-timing/#sec-window.performance-attribute",assert:"The window.performance attribute provides a hosting area for performance related attributes. "});
+    }
+  }
+
+  test(func, msg, properties);
+}
+
+function test_true(value, msg, properties)
+{
+  wp_test(function () { assert_true(value, msg); }, msg, properties);
+}
+
+function test_equals(value, equals, msg, properties)
+{
+  wp_test(function () { assert_equals(value, equals, msg); }, msg, properties);
+}