refactor($rootScope): simplify $emit stopPropagation handling

src/ng/rootScope.js

@@ -1235,8 +1235,7 @@ function $RootScopeProvider() {
 
           //if any listener on the current scope stops propagation, prevent bubbling
           if (stopPropagation) {
-            event.currentScope = null;
-            return event;
+            break;
           }
           //traverse upwards
           scope = scope.$parent;