views_handler_field_history_user_timestamp::render() should look at date changed instead of created as in node_mark

I found that views_handler_field_history_user_timestamp didn't mark nodes as new which weren't filtered by 'Show only content that is new or updated' (views_handler_filter_history_user_timestamp).

The reason is that views_handler_filter_history_user_timestamp refers to the changed date while views_handler_field_history_user_timestamp refers to created date.

node_mark() from node.module also uses the changed date to mark content as new. ... Using the changed date to mark content as new makes completely sense, because it does not matter when it was created, for the user who hasn't read a changed content, this content always will be new to him.