Add blink-side binding code for navigator.serviceWorker.current

LayoutTests/http/tests/serviceworker/resources/test-helpers.js

Index: LayoutTests/http/tests/serviceworker/resources/test-helpers.js
diff --git a/LayoutTests/http/tests/serviceworker/resources/test-helpers.js b/LayoutTests/http/tests/serviceworker/resources/test-helpers.js
index c4df888078ec3df7853796bf91ca1b8b14595198..83b0391ab032ac27464d413e7b397e45f66e686b 100644
--- a/LayoutTests/http/tests/serviceworker/resources/test-helpers.js
+++ b/LayoutTests/http/tests/serviceworker/resources/test-helpers.js
@@ -10,9 +10,8 @@ function service_worker_test(url, description) {
                 messageChannel.port1.onmessage = t.step_func(onMessage);
                 worker.postMessage({port:messageChannel.port2}, [messageChannel.port2]);
             }),
-            t.step_func(function(reason) {
-                assert_unreached('Registration should succeed, but failed: ' + reason.name);
-            }));
+            unreached_rejection(t, 'Registration should succeed, but failed')
+        );
 
         function onMessage(e) {
             assert_equals(e.data, 'pass');
@@ -31,3 +30,10 @@ function unreached_func(test, desc) {
         assert_unreached(desc);
     });
 }
+
+// Rejection-specific helper that provides more details
+function unreached_rejection(test, prefix) {
+    return test.step_func(function(reason) {
+        assert_unreached(prefix + ': ' + reason.name);
+    });
+}