title: Dataflow fusion + windows/triggers
body: <p>I'm aware that Dataflow can modify a pipeline's execution graph through <a href="https://cloud.google.com/dataflow/service/dataflow-service-desc#fusion-optimization" rel="nofollow noreferrer">Fusion Optimization</a>.</p>
  
  <p>Do windows/triggers factor in at all to fusion optimization?</p>
  
  <p>Does a streaming pipeline and/or unbounded sources (Pub/Sub) influence that behavior at all?</p>