Add GetPropertyAttribute method for Object in the API

src/objects.cc

Index: src/objects.cc
diff --git a/src/objects.cc b/src/objects.cc
index 26ab64552fc344fff7be569d3f43b365650c4d6f..94ee4ece8bbda91524defc5363edc1daabac5bcf 100644
--- a/src/objects.cc
+++ b/src/objects.cc
@@ -2639,6 +2639,27 @@ PropertyAttributes JSReceiver::GetPropertyAttribute(JSReceiver* receiver,
 }
 
 
+PropertyAttributes JSReceiver::TryGetPropertyAttribute(
+    Handle<Object> key,
+    bool* has_pending_exception) {
+  Isolate* isolate = GetIsolate();
+  HandleScope scope(isolate);
+  Handle<String> name;
+  if (key->IsString()) {
+    name = Handle<String>::cast(key);
+  } else {
+    Handle<Object> converted =
+        Execution::ToString(key, has_pending_exception);
+    if (*has_pending_exception) return NONE;
+    name = Handle<String>::cast(converted);
+  }
+  PropertyAttributes attr = GetPropertyAttributeWithReceiver(this, *name);
+  // Returns NONE when the property doesn't exist.
+  if (attr == ABSENT) return NONE;
+  return attr;
+}
+
+
 PropertyAttributes JSReceiver::GetLocalPropertyAttribute(String* name) {
   // Check whether the name is an array index.
   uint32_t index = 0;