Add native callbacks to FastAccessorAssembler.

src/api-experimental.cc

Index: src/api-experimental.cc
diff --git a/src/api-experimental.cc b/src/api-experimental.cc
index 2b49e9723a57458737561c1c26c9a3621b4639c3..9b3ce2c815aadac6aeeea0021e5905c5193458c1 100644
--- a/src/api-experimental.cc
+++ b/src/api-experimental.cc
@@ -122,5 +122,11 @@ void FastAccessorBuilder::CheckNotZeroOrJump(ValueId value_id,
   FromApi(this)->CheckNotZeroOrJump(value_id, label_id);
 }
 
+
+FastAccessorBuilder::ValueId FastAccessorBuilder::Call(
+    v8::FunctionCallback callback, ValueId value_id) {
+  return FromApi(this)->Call(callback, value_id);
+}
+
 }  // namespace experimental
 }  // namespace v8