[strong] Implement per-object restrictions behaviour of delete operator

src/elements.cc

Index: src/elements.cc
diff --git a/src/elements.cc b/src/elements.cc
index 0237a97f4bc73311a1747b5a763d374b8a192912..2e9f36863f847d75a9460a6f96030b2c4fc3cc47 100644
--- a/src/elements.cc
+++ b/src/elements.cc
@@ -1401,8 +1401,8 @@ class DictionaryElementsAccessor
         Handle<SeededNumberDictionary>::cast(backing_store);
     int entry = dictionary->FindEntry(key);
     if (entry != SeededNumberDictionary::kNotFound) {
-      Handle<Object> result =
-          SeededNumberDictionary::DeleteProperty(dictionary, entry);
+      Handle<Object> result = SeededNumberDictionary::DeleteProperty(
+          dictionary, entry, obj->map()->is_strong());

[rossberg, 2015/05/22 14:01:26]

Do we have to pass down the flag here? It seems that if the object is strong,
there is no point in even making the call, and you can immediately set the
result to false right here.

[conradw, 2015/05/27 18:09:32]

Yes, missed this.

       if (*result == *isolate->factory()->false_value()) {
         if (is_strict(language_mode)) {
           // Deleting a non-configurable property in strict mode.