Port r9030 and part of r9016 to 3.3 branch.

src/v8natives.js

Index: src/v8natives.js
diff --git a/src/v8natives.js b/src/v8natives.js
index e27f3b00a34a94375d12eee1aafbdc6f78076532..700fe5889c89c4e4eddfd79b1e5060a15b67b152 100644
--- a/src/v8natives.js
+++ b/src/v8natives.js
@@ -326,18 +326,18 @@ function IsInconsistentDescriptor(desc) {
 // ES5 8.10.4
 function FromPropertyDescriptor(desc) {
   if (IS_UNDEFINED(desc)) return desc;
-  var obj = new $Object();
+
   if (IsDataDescriptor(desc)) {
-    obj.value = desc.getValue();
-    obj.writable = desc.isWritable();
-  }
-  if (IsAccessorDescriptor(desc)) {
-    obj.get = desc.getGet();
-    obj.set = desc.getSet();
-  }
-  obj.enumerable = desc.isEnumerable();
-  obj.configurable = desc.isConfigurable();
-  return obj;
+    return { value: desc.getValue(),
+             writable: desc.isWritable(),
+             enumerable: desc.isEnumerable(),
+             configurable: desc.isConfigurable() };
+  }
+  // Must be an AccessorDescriptor then. We never return a generic descriptor.
+  return { get: desc.getGet(),
+           set: desc.getSet(),
+           enumerable: desc.isEnumerable(),
+           configurable: desc.isConfigurable() };
 }
 
 // ES5 8.10.5.