title: Generating async Javascript events from browser plugin (NPAPI)
body: <p>I'm writing a web browser plugin (NPAPI.)</p>
  
  <p>My plugin starts a worker thread, and as the worker progresses, I'd like to pass events back to Javascript. But because of the NPAPI threading model, it's not legal for the worker thread to call back into NPAPI directly, so the worker thread can't invoke Javascript.</p>
  
  <p>One solution to this is the NPN_PluginThreadAsyncCall function. But this is a relatively new function. For example, it's supported only from Firefox 3 on.</p>
  
  <p>Is there any way to get async event delivery/javascript execution from an NPAPI plugin without using NPN_PluginThreadAsyncCall? What did people do before this function was added?</p>