Support performance.now() in workers.

LayoutTests/http/tests/w3c/webperf/resources/worker.js

Index: LayoutTests/http/tests/w3c/webperf/resources/worker.js
diff --git a/LayoutTests/http/tests/w3c/webperf/resources/worker.js b/LayoutTests/http/tests/w3c/webperf/resources/worker.js
new file mode 100644
index 0000000000000000000000000000000000000000..1e3e58cf692c72c346a590c6e3b58572a8ea6882
--- /dev/null
+++ b/LayoutTests/http/tests/w3c/webperf/resources/worker.js
@@ -0,0 +1,26 @@
+function runTests(event) {
+  var tests = event.data;
+  var results = [];
+  for (var i = 0; i < tests.length; i++) {
+    try {
+      results.push(eval(tests[i]));
+    } catch(e) {
+      results.push(e);
+    }
+  }
+  return results;
+}
+
+self.onmessage = function(event) {
+  var results = runTests(event);
+  postMessage(results);
+  self.close();
+};
+
+self.addEventListener("connect", function(event) {
+  var port = event.ports[0];
+  port.onmessage = function(event) {
+    var results = runTests(event);
+    port.postMessage(results);
+  };
+});