add interceptors which do not mask existing properties

src/lookup-inl.h

Index: src/lookup-inl.h
diff --git a/src/lookup-inl.h b/src/lookup-inl.h
index 50f4b0fcc9ddad89849b64fa71183077f8f97480..18bcbc50c5de7c2729fd771247980dcdc1e37764 100644
--- a/src/lookup-inl.h
+++ b/src/lookup-inl.h
@@ -31,10 +31,13 @@ JSReceiver* LookupIterator::NextHolder(Map* map) {
 }
 
 
-LookupIterator::State LookupIterator::LookupInHolder(Map* map,
-                                                     JSReceiver* holder) {
+LookupIterator::State LookupIterator::LookupInHolder(Map* const map,
+                                                     JSReceiver* const holder) {
   STATIC_ASSERT(INTERCEPTOR == BEFORE_PROPERTY);
   DisallowHeapAllocation no_gc;
+  if (interceptor_state_ == InterceptorState::kProcessNonMasking) {
+    return LookupNonMaskingInterceptorInHolder(map, holder);
+  }
   switch (state_) {
     case NOT_FOUND:
       if (map->IsJSProxyMap()) return JSPROXY;
@@ -44,7 +47,8 @@ LookupIterator::State LookupIterator::LookupInHolder(Map* map,
       }
     // Fall through.
     case ACCESS_CHECK:
-      if (check_interceptor() && map->has_named_interceptor()) {
+      if (check_interceptor() && map->has_named_interceptor() &&
+          !SkipInterceptor(JSObject::cast(holder))) {
         return INTERCEPTOR;
       }
     // Fall through.
@@ -82,6 +86,29 @@ LookupIterator::State LookupIterator::LookupInHolder(Map* map,
   UNREACHABLE();
   return state_;
 }
+
+
+LookupIterator::State LookupIterator::LookupNonMaskingInterceptorInHolder(
+    Map* const map, JSReceiver* const holder) {
+  switch (state_) {
+    case NOT_FOUND:
+      if (map->is_access_check_needed() &&
+          !isolate_->IsInternallyUsedPropertyName(name_)) {

[Toon Verwaest, 2015/03/11 14:09:35]

You don't need these, given that you had to have access to the entire chain to
get here.

+        return ACCESS_CHECK;
+      }
+    // Fall through.
+    case ACCESS_CHECK:
+      if (check_interceptor() && map->has_named_interceptor() &&
+          !SkipInterceptor(JSObject::cast(holder))) {
+        return INTERCEPTOR;
+      }
+    // Fall through.
+    default:
+      return NOT_FOUND;
+  }
+  UNREACHABLE();
+  return state_;
+}
 }
 }  // namespace v8::internal