[es6] Fix Object built-in subclassing.

src/js/v8natives.js

Index: src/js/v8natives.js
diff --git a/src/js/v8natives.js b/src/js/v8natives.js
index dae087ded436e361b2610e8d99c634d6aace27a2..8faf757adcd1977ec5465e35af79c084f538e201 100644
--- a/src/js/v8natives.js
+++ b/src/js/v8natives.js
@@ -1322,14 +1322,13 @@ function ObjectSetProto(proto) {
 }
 
 
+// ECMA-262, Edition 6, section 19.1.1.1
 function ObjectConstructor(x) {
-  if (%_IsConstructCall()) {
-    if (x == null) return this;
-    return TO_OBJECT(x);
-  } else {
-    if (x == null) return { };
-    return TO_OBJECT(x);
+  if (GlobalObject != new.target && !IS_UNDEFINED(new.target)) {

[Michael Starzinger, 2015/10/30 11:52:26]

Benedikt raised the question: Does this deal with "undetectable" objects
correctly?

+    return this;
   }
+  if (IS_NULL(x) || IS_UNDEFINED(x)) return {};
+  return TO_OBJECT(x);
 }