Add event.stopped, a boolean that is set to when Event#stop is called.

src/event.js

@@ -82,8 +82,9 @@ Event.Methods = (function() {
 
     stop: function(event) {
       Event.extend(event);
-      event.preventDefault(); 
-      event.stopPropagation(); 
+      event.preventDefault();
+      event.stopPropagation();
+      event.stopped = true;
     }
   };
 })();

test/unit/event.html

@@ -208,8 +208,23 @@
       assert(eventResults.windowLoad, "windowLoad");
       assert(eventResults.windowLoad.endOfDocument, "windowLoad.endOfDocument");
       assert(eventResults.windowLoad.contentLoaded, "windowLoad.contentLoaded");
+    }},
+    
+    testEventStopped: function() { with(this) {
+      var span = $("span"), event;
+
+      span.observe("test:somethingHappened", function() { });
+      event = span.fire("test:somethingHappened");
+      assert(!event.stopped, "event.stopped should be false with an empty observer");
+      span.stopObserving("test:somethingHappened");
+      
+      span.observe("test:somethingHappened", function(e) { e.stop() });
+      event = span.fire("test:somethingHappened");
+      assert(event.stopped, "event.stopped should be true for an observer that calls stop");
+      span.stopObserving("test:somethingHappened");
     }}
     
+    
   }, 'testlog');
 
   document.observe("dom:loaded", function(event) {