Remove support for PushSubscription.subscriptionId.

LayoutTests/http/tests/push_messaging/resources/instrumentation-service-worker.js

Index: LayoutTests/http/tests/push_messaging/resources/instrumentation-service-worker.js
diff --git a/LayoutTests/http/tests/push_messaging/resources/instrumentation-service-worker.js b/LayoutTests/http/tests/push_messaging/resources/instrumentation-service-worker.js
index 81634ca362c48ffe81ef904cfa0dc86433eb39fc..f635b2c97eda8cf6f1098a29576ee3983bc0950b 100644
--- a/LayoutTests/http/tests/push_messaging/resources/instrumentation-service-worker.js
+++ b/LayoutTests/http/tests/push_messaging/resources/instrumentation-service-worker.js
@@ -28,7 +28,6 @@ self.addEventListener('message', function(workerEvent) {
                     lastSeenSubscription = subscription;
                     port.postMessage({ command: event.data.command,
                                        success: true,
-                                       subscriptionId: subscription.subscriptionId,
                                        endpoint: subscription.endpoint });
                 }).catch(makeErrorHandler(event.data.command));
                 break;
@@ -36,10 +35,10 @@ self.addEventListener('message', function(workerEvent) {
             case 'getSubscription':
                 self.registration.pushManager.getSubscription().then(function(subscription) {
                     lastSeenSubscription = subscription;
-                    var subscriptionId = subscription ? subscription.subscriptionId : null;
+                    var endpoint = subscription ? subscription.endpoint : null;
                     port.postMessage({ command: event.data.command,
                                        success: true,
-                                       subscriptionId: subscriptionId });
+                                       endpoint: endpoint });
                 }).catch(makeErrorHandler(event.data.command));
                 break;