Add Function based profile tree

runtime/observatory/lib/src/app/location_manager.dart

Index: runtime/observatory/lib/src/app/location_manager.dart
diff --git a/runtime/observatory/lib/src/app/location_manager.dart b/runtime/observatory/lib/src/app/location_manager.dart
index 38269dfff23e49e408cc1b10f8134d6a706fc874..86e71e5ef9ab2f11b911e3df655cb789aeb1dd02 100644
--- a/runtime/observatory/lib/src/app/location_manager.dart
+++ b/runtime/observatory/lib/src/app/location_manager.dart
@@ -76,7 +76,8 @@ abstract class LocationManager extends Observable {
   }
 
   /// Handle clicking on an application url link.
-  void onGoto(MouseEvent event, var detail, Element target) {
+  void onGoto(MouseEvent event) {
+    var target = event.target;
     var href = target.attributes['href'];
     if (event.button > 0 || event.metaKey || event.ctrlKey ||
         event.shiftKey || event.altKey) {