 pageCache               = {}
 cacheSize               = 10
 transitionCacheEnabled  = false
+progressBar             = null
 
 currentState            = null
 loadedAssets            = null

  visit,
  pagesCached,
  enableTransitionCache,
  allowLinkExtensions: Link.allowExtensions,
  supported: browserSupportsTurbolinks,
  EVENTS: clone(EVENTS)


  rememberReferer()
  cacheCurrentPage()
  progressBar?.start()

  if transitionCacheEnabled and cachedPage = transitionCacheFor(url.absolute)
    fetchHistory cachedPage
    fetchReplacement url, null, false
  else
    fetchReplacement url, resetScrollPosition

