[es6] Partially implement Reflect.preventExtensions.

src/builtins.cc

Index: src/builtins.cc
diff --git a/src/builtins.cc b/src/builtins.cc
index b672185792c417a75f311c7ea6b35d880f91f6a4..ce603bd7f7cca34aa3f42194ce45bc5ee8401f96 100644
--- a/src/builtins.cc
+++ b/src/builtins.cc
@@ -1554,6 +1554,32 @@ BUILTIN(ReflectIsExtensible) {
 }
 
 
+// ES6 section 26.1.12 Reflect.preventExtensions
+BUILTIN(ReflectPreventExtensions) {
+  HandleScope scope(isolate);
+  DCHECK_EQ(2, args.length());
+  Handle<Object> target = args.at<Object>(1);
+
+  if (!target->IsJSReceiver()) {
+    THROW_NEW_ERROR_RETURN_FAILURE(
+        isolate, NewTypeError(MessageTemplate::kCalledOnNonObject,
+                              isolate->factory()->NewStringFromAsciiChecked(
+                                  "Reflect.preventExtensions")));
+  }
+
+  // TODO(neis): For now, we ignore proxies.

[rossberg, 2015/10/15 10:54:40]

Actually, the case distinction should not be made here, it should be in a new
method JSReceiver::PreventExtensions. The same probably goes for all other
Reflect methods.

+
+  if (target->IsJSObject()) {
+    bool result;
+    MAYBE_ASSIGN_RETURN_ON_EXCEPTION(
+        isolate, bool, result,
+        JSObject::PreventExtensionsInternal(Handle<JSObject>::cast(target)));
+    return *isolate->factory()->ToBoolean(result);
+  }
+  return *isolate->factory()->false_value();
+}
+
+
 // ES6 section 20.3.4.45 Date.prototype [ @@toPrimitive ] ( hint )
 BUILTIN(DateToPrimitive) {
   HandleScope scope(isolate);