Make Try Dart tests run on Firefox.

dart/site/try/src/cache.dart

 // Copyright (c) 2013, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 library trydart.cache;
 
 import 'dart:async' show
     Timer;
 
 import 'dart:html' show
     AnchorElement,
     ApplicationCache,
     Event,
     MeterElement,
     ProgressEvent,
     window;
 
 import 'ui.dart' show
     cacheStatusElement;
 
 /// Called when the window has finished loading.
 void onLoad(Event event) {
-  window.applicationCache.onUpdateReady.listen((_) => updateCacheStatus());
-  window.applicationCache.onCached.listen((_) => updateCacheStatus());
-  window.applicationCache.onChecking.listen((_) => updateCacheStatus());
-  window.applicationCache.onDownloading.listen((_) => updateCacheStatus());
-  window.applicationCache.onError.listen((_) => updateCacheStatus());
-  window.applicationCache.onNoUpdate.listen((_) => updateCacheStatus());
-  window.applicationCache.onObsolete.listen((_) => updateCacheStatus());
+  if (!ApplicationCache.supported) return;
+  window.applicationCache.onUpdateReady.listen(updateCacheStatus);
+  window.applicationCache.onCached.listen(updateCacheStatus);
+  window.applicationCache.onChecking.listen(updateCacheStatus);
+  window.applicationCache.onDownloading.listen(updateCacheStatus);
+  window.applicationCache.onError.listen(updateCacheStatus);
+  window.applicationCache.onNoUpdate.listen(updateCacheStatus);
+  window.applicationCache.onObsolete.listen(updateCacheStatus);
   window.applicationCache.onProgress.listen(onCacheProgress);
 }
 
-onCacheProgress(ProgressEvent event) {
-  if (!event.lengthComputable) {
-    updateCacheStatus();
-    return;
+void onCacheProgress(Event event) {
+  if (event is ProgressEvent) {
+    // Firefox doesn't fire a ProgressEvent on cache progress.  Just a plain
+    // Event with type == "progress".
+    if (event.lengthComputable) {
+      updateCacheStatusFromEvent(event);
+      return;
+    }
   }
+  updateCacheStatus(null);
+}
+
+void updateCacheStatusFromEvent(ProgressEvent event) {
   cacheStatusElement.nodes.clear();
   cacheStatusElement.appendText('Downloading SDK ');
   var progress = '${event.loaded} of ${event.total}';
   if (MeterElement.supported) {
     cacheStatusElement.append(
         new MeterElement()
             ..appendText(progress)
             ..min = 0
             ..max = event.total
             ..value = event.loaded);
   } else {
     cacheStatusElement.appendText(progress);
   }
 }
 
 String cacheStatus() {
   if (!ApplicationCache.supported) return 'offline not supported';
   int status = window.applicationCache.status;
   if (status == ApplicationCache.CHECKING) return 'Checking for updates';
   if (status == ApplicationCache.DOWNLOADING) return 'Downloading SDK';
   if (status == ApplicationCache.IDLE) return 'Try Dart! works offline';
   if (status == ApplicationCache.OBSOLETE) return 'OBSOLETE';
   if (status == ApplicationCache.UNCACHED) return 'offline not available';
   if (status == ApplicationCache.UPDATEREADY) return 'SDK downloaded';
   return '?';
 }
 
-void updateCacheStatus() {
+void updateCacheStatus(_) {
   cacheStatusElement.nodes.clear();
   int status = window.applicationCache.status;
   if (status == ApplicationCache.UPDATEREADY) {
     cacheStatusElement.appendText('New version of Try Dart! ready: ');
     cacheStatusElement.append(
         new AnchorElement(href: '#')
             ..appendText('Load')
             ..onClick.listen((event) {
               event.preventDefault();
               window.applicationCache.swapCache();
               window.location.reload();
             }));
   } else if (status == ApplicationCache.IDLE) {
     cacheStatusElement.appendText(cacheStatus());
     cacheStatusElement.classes.add('offlineyay');
     new Timer(const Duration(seconds: 10), () {
       cacheStatusElement.style.display = 'none';
     });
   } else {
     cacheStatusElement.appendText(cacheStatus());
   }
 }