This opensource extension adds notification popups for downloads. It does not disable the download shelf. For that I recommend https://chrome.google.com/webstore/detail/download-notifier/gdekiloeocnfnochnkldpkmllmfiaeke The code is licensed under GPLV3 and available at https://github.com/aadfPT/ChromeDownloadNotifications
You can Follow the below Step By Step procedure to install the Download Notifications Chrome Extension to your Chrome Web browser.
It is the Download Notifications Chrome extension download link you can download and install Chrome Browser.
Simple Download Manager
A lightweight & efficient extension of Chrome’s Download Manager.
A useful download manager extension
You get a desktop notification while your downloading finished.
Easily manage all your downloads from toolbar popup!
This extension hides annoying downloads bar in the bottom of the screen.
Hides the download shelf when all downloads complete
Easily manage your downloads in status-bar.
Easily open downloads in a new tab via the toolbar button.
Open the Download Manager with just one click.