Service Worker: Fix getRegistrations.html layout test.

LayoutTests/http/tests/serviceworker/resources/frame-for-getregistrations.html

Index: LayoutTests/http/tests/serviceworker/resources/frame-for-getregistrations.html
diff --git a/LayoutTests/http/tests/serviceworker/resources/frame-for-getregistrations.html b/LayoutTests/http/tests/serviceworker/resources/frame-for-getregistrations.html
index 511bd972090cc01e0bed798a2b2e6ac65b37ebc2..474004ff0a959c95372fe0ca29941ebad0bad092 100644
--- a/LayoutTests/http/tests/serviceworker/resources/frame-for-getregistrations.html
+++ b/LayoutTests/http/tests/serviceworker/resources/frame-for-getregistrations.html
@@ -4,16 +4,27 @@
 var scope = 'scope-for-getregistrations';
 var script = 'empty-worker.js';
 var registration;
-
-navigator.serviceWorker.register(script, { scope: scope })
-  .then(function(r) { registration = r; });
+var port;
 
 self.onmessage = function(e) {
-  if (e.data == 'unregister') {
-    registration.unregister()
-      .then(function() {
-          e.ports[0].postMessage('unregistered');
-        });
+  if (e.data == 'register') {
+    port = e.ports[0];
+    port.onmessage = function(e) {
+      if (e.data == 'unregister') {
+        registration.unregister()
+          .then(function() {
+              port.postMessage('unregistered');
+            });
+      }
+    };
   }
+
+  // Frame registers a registration scoped
+  // http://localhost:8000/serviceworker/resources/scope-for-getregistrations
+  navigator.serviceWorker.register(script, { scope: scope })
+    .then(function(r) {
+        registration = r;
+        e.ports[0].postMessage('registered');
+      });
 };
 </script>