Reject push registrations when no sender Id has been provided.

chrome/test/data/push_messaging/test.html

Index: chrome/test/data/push_messaging/test.html
diff --git a/chrome/test/data/push_messaging/test.html b/chrome/test/data/push_messaging/test.html
index 3ad79289188b69afc420915c08652c6fad71b372..372f3e1c7978121d103d6c8827025794cb4c97a3 100644
--- a/chrome/test/data/push_messaging/test.html
+++ b/chrome/test/data/push_messaging/test.html
@@ -55,6 +55,15 @@
           }, sendErrorToTest);
     }
 
+    function removeManifest() {
+      var element = document.querySelector('link[rel="manifest"]');
+      if (element) {
+        element.parentNode.removeChild(element);
+        sendResultToTest('manifest removed');
+      } else
+        sendResultToTest('unable to find manifest element');
+    }
+
     function registerPush() {
       navigator.serviceWorker.ready.then(function() {
         navigator.push.register().then(function(pushRegistration) {