Called when a download's status or progress information has been updated.
This may be called multiple times before and after on_before_download().
Execute |callback| either asynchronously or in this function to cancel the
download if desired. Do not keep a reference to |download_item| outside of
this function.
Called when a download's status or progress information has been updated. This may be called multiple times before and after on_before_download(). Execute |callback| either asynchronously or in this function to cancel the download if desired. Do not keep a reference to |download_item| outside of this function.