ServiceWorker: Implement 'source' and 'origin' attributes of ExtendableMessageEvent

third_party/WebKit/LayoutTests/http/tests/serviceworker/fetch-event-respond-with-stops-propagation.html

Index: third_party/WebKit/LayoutTests/http/tests/serviceworker/fetch-event-respond-with-stops-propagation.html
diff --git a/third_party/WebKit/LayoutTests/http/tests/serviceworker/fetch-event-respond-with-stops-propagation.html b/third_party/WebKit/LayoutTests/http/tests/serviceworker/fetch-event-respond-with-stops-propagation.html
index 20629ef05b0c7bd04d6e8e648ade9c02cefa3214..d49ceed95d1c7a03e4c4cfb49fd1ccf0333ef862 100644
--- a/third_party/WebKit/LayoutTests/http/tests/serviceworker/fetch-event-respond-with-stops-propagation.html
+++ b/third_party/WebKit/LayoutTests/http/tests/serviceworker/fetch-event-respond-with-stops-propagation.html
@@ -17,13 +17,13 @@ promise_test(function(t) {
           return with_iframe(scope);
         })
       .then(function(frame) {
+          add_completion_callback(function() { frame.remove(); });
           var channel = new MessageChannel();
           var saw_message = new Promise(function(resolve) {
               channel.port1.onmessage = function(e) { resolve(e.data); }
             });
           var worker = frame.contentWindow.navigator.serviceWorker.controller;
 
-          frame.remove();
           worker.postMessage({port: channel.port2}, [channel.port2]);
           return saw_message;
         })