Add C++ implementation of Object.defineProperties

src/v8natives.js

Index: src/v8natives.js
diff --git a/src/v8natives.js b/src/v8natives.js
index 168f97b91add2c5ac868bffb6842b56104f850ad..95a7193b8ae7490902bf493785999adfaa7a4919 100644
--- a/src/v8natives.js
+++ b/src/v8natives.js
@@ -1089,19 +1089,24 @@ function GetOwnEnumerablePropertyNames(object) {
 
 // ES5 section 15.2.3.7.
 function ObjectDefineProperties(obj, properties) {
-  if (!IS_SPEC_OBJECT(obj)) {
-    throw MakeTypeError(kCalledOnNonObject, "Object.defineProperties");
-  }
-  var props = TO_OBJECT(properties);
-  var names = GetOwnEnumerablePropertyNames(props);
-  var descriptors = new InternalArray();
-  for (var i = 0; i < names.length; i++) {
-    descriptors.push(ToPropertyDescriptor(props[names[i]]));
-  }
-  for (var i = 0; i < names.length; i++) {
-    DefineOwnProperty(obj, names[i], descriptors[i], true);
+  // The new pure-C++ implementation doesn't support Proxies yet, nor O.o.
+  // TODO(jkummerow): Implement missing features and remove fallback path.
+  if (%_IsJSProxy(obj) || %_IsJSProxy(properties) || %IsObserved(obj)) {
+    if (!IS_SPEC_OBJECT(obj)) {
+      throw MakeTypeError(kCalledOnNonObject, "Object.defineProperties");
+    }
+    var props = TO_OBJECT(properties);
+    var names = GetOwnEnumerablePropertyNames(props);
+    var descriptors = new InternalArray();
+    for (var i = 0; i < names.length; i++) {
+      descriptors.push(ToPropertyDescriptor(props[names[i]]));
+    }
+    for (var i = 0; i < names.length; i++) {
+      DefineOwnProperty(obj, names[i], descriptors[i], true);
+    }
+    return obj;
   }
-  return obj;
+  return %ObjectDefineProperties(obj, properties);
 }