Fixing another case of multiple upgrades of a custom element

Source/bindings/dart/DartDOMWrapper.h

Index: Source/bindings/dart/DartDOMWrapper.h
diff --git a/Source/bindings/dart/DartDOMWrapper.h b/Source/bindings/dart/DartDOMWrapper.h
index ce7b9dd0877ad4ffd0c6cca14afc54deffe9326e..c74f6f65cda84dc4ab160f8e52af953d1235745b 100644
--- a/Source/bindings/dart/DartDOMWrapper.h
+++ b/Source/bindings/dart/DartDOMWrapper.h
@@ -272,11 +272,17 @@ private:
     }
 
     template <class BindingsClass>
-    static void wrapperWeakCallback(Dart_WeakPersistentHandle, void* peer)
+    static void wrapperWeakCallback(Dart_WeakPersistentHandle wrapper, void* peer)
     {
         typedef DartDOMWrapperTraits<BindingsClass> Traits;
         DartDOMData* domData = DartDOMData::current();
         typename BindingsClass::NativeType* domObject = static_cast<typename BindingsClass::NativeType*>(peer);
+        Dart_WeakPersistentHandle currentWrapper = Traits::MapTraits::domMap(domData)->get(domObject);
+        // This could be an old wrapper which has been replaced with a custom element.
+        if (!Dart_IdentityEquals(Dart_HandleFromWeakPersistent(currentWrapper), Dart_HandleFromWeakPersistent(wrapper))) {

[blois, 2013/10/31 18:43:07]

Changing the check to:
if (currentWrapper != wrapper) {}

Appears to fix the issue as well. Not sure which one exactly is preferred here.

[siva, 2013/10/31 19:42:40]

if (currentWrapper != wrapper) {} is preferable for efficiency purposes. You
could write it as:

if (currentWrapper != wrapper) {
  ASSERT(!Dart_IdentityEquals(Dart_HandleFromWeakPersistent......);
  return;
}


I am assuming that currentWrapper was also created in the same path using
associateWrapper and it is a PrologueWeakPersistentHandle

[blois, 2013/10/31 20:24:18]

Done.

+            return;
+        }
+
         if (DartDOMWrapperTraits<BindingsClass>::MapTraits::domMap(domData)->contains(domObject)) {
             Traits::MapTraits::domMap(domData)->remove(domObject);
             Traits::ActiveTraits::removeWrapper(domData, domObject);