Trying an approach that adds a "loading" method when plugin.js is first loaded to give us a bit more time to initialize the plugin before calling connect. Currently the all new timeout is 60 seconds instead of 5 seconds.
Bug 447738 - small fix to previous commit. Add test stub.
Bug 447738 - Unminified JS plugin times out

* Create PluginProvider early, defer loading of javascriptPlugin's deps
  until later.
* Rename javascriptWorker to javascriptBootstrap, since it is used in both
  Worker and non-Worker cases now.