code: private void pushScript(ScriptDescription newCurrentScript) {
      currentScript = newCurrentScript;
      if (!scriptStack.isEmpty()) {
        ScriptDescription parentScript = scriptStack.peek();
        parentScript.addChildScript(currentScript);
      }
      scriptStack.addFirst(currentScript);
    }
docs: Record the provided script as the current script at top of the script stack and add it as a
  child of the previous current script if there was one.
  
  <p>Keeping track of the current script facilitates aggregation of accurate script state so that
  rewriting can run properly. Handles scripts and nested goog.modules.