Use a .worker.js test

tests/wpt/metadata/MANIFEST.json

     "deleted": [],
     "items": {
       "testharness": {
-        "websockets/Send-data-worker.htm": [
+        "websockets/Send-data.worker.js": [
           {
-            "path": "websockets/Send-data-worker.htm",
-            "url": "/websockets/Send-data-worker.htm"
+            "path": "websockets/Send-data.worker.js",
+            "url": "/websockets/Send-data.worker"
           }
         ]
       }

tests/wpt/web-platform-tests/websockets/Send-data.worker.js

@@ -0,0 +1,21 @@
+importScripts("/resources/testharness.js");
+importScripts('websocket.js?pipe=sub')
+
+var data = "test data";
+
+async_test(function(t) {
+
+    var wsocket = CreateWebSocket(false, false, false);
+
+    wsocket.addEventListener('open', function (e) {
+        wsocket.send(data)
+    }, true)
+
+    wsocket.addEventListener('message', t.step_func_done(function(e) {
+            assert_equals(e.data, data);
+            done();
+    }), true);
+
+}, "W3C WebSocket API - Send data on a WebSocket in a Worker")
+
+