一旦确定了文件名 onDeterminingFilename 事件
被触发，调用回调函数并且需要2
参数

• As soon as the filename is determined onDeterminingFilename event is triggered upon which a callback function is called and it takes 2 parameters

  
  
  1. item 包含下载ID，url，文件名，引用等数据的对象。 （请参阅
     https://developer.chrome.com/extensions/downloads#type -DownloadItem ）
  
  
  2. __建议必须同步或异步传递建议。
  
  
  1. item object which contains data such as download id, url, filename, referrer etc. (see https://developer.chrome.com/extensions/downloads#type-DownloadItem)
  2. __suggest which must be called to pass suggestion either synchronously or asynchronously.



• 定义了一个建议函数，该函数将用于根据特定规则调用 __ suggest
  


• 全部该规则从本地内存访问， for 循环运行
  迭代它们。


• 对于每次迭代，基于规则中的操作数据使用特定的文件名调用
suggest函数和
  conflictAction 。