Expose performance.memory 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
index 1e3e58cf692c72c346a590c6e3b58572a8ea6882..5ed58a7ceff35bb2fb5ec9cf73a66913c5d6205b 100644
--- a/LayoutTests/http/tests/w3c/webperf/resources/worker.js
+++ b/LayoutTests/http/tests/w3c/webperf/resources/worker.js
@@ -13,7 +13,7 @@ function runTests(event) {
 
 self.onmessage = function(event) {
   var results = runTests(event);
-  postMessage(results);
+  postMessage(JSON.stringify(results));
   self.close();
 };
 
@@ -21,6 +21,6 @@ self.addEventListener("connect", function(event) {
   var port = event.ports[0];
   port.onmessage = function(event) {
     var results = runTests(event);
-    port.postMessage(results);
+    port.postMessage(JSON.stringify(results));
   };
 });