       @_referenceCounts[url]--
       if @_referenceCounts[url] == 0
         delete @_cache[url]
+        delete @_loaded[url]
         true
       else
         false

    constructor: ->
      @_cache = {}
      @_referenceCounts = {}

    # OUT: promise.then (bitmap) ->
    get: (url, initializerPromise) ->

      validate:   (v) -> !v || isString v
      postSetter: (v) -> v && @_loadBitmapFromSource v

    altSources:
      default:    null
      validate:   (v) -> !v || isPlainArray v

  _loadBitmapFromSource: (source) ->
    sourceToBitmapCache.get source
    .then (bitmap) =>
