Use LookupIterator for GetElementAttributes and friends

src/lookup.cc

Index: src/lookup.cc
diff --git a/src/lookup.cc b/src/lookup.cc
index 38cc522c6e0833fb740b9a8cbb00fd88d8e3d185..aa66d152e39a9cae781a9978f6fa2facecac6825 100644
--- a/src/lookup.cc
+++ b/src/lookup.cc
@@ -264,6 +264,13 @@ Handle<Object> LookupIterator::FetchValue() const {
   Handle<JSObject> holder = GetHolder<JSObject>();
   if (IsElement()) {
     // TODO(verwaest): Optimize.
+    if (holder->IsStringObjectWithCharacterAt(index_)) {
+      Handle<JSValue> js_value = Handle<JSValue>::cast(holder);
+      Handle<String> string(String::cast(js_value->value()));
+      return factory()->LookupSingleCharacterStringFromCode(
+          String::Flatten(string)->Get(index_));
+    }
+
     ElementsAccessor* accessor = holder->GetElementsAccessor();
     return accessor->Get(holder, index_);
   } else if (holder_map_->IsGlobalObjectMap()) {