Same is true for removing individual downloads.

Also reproduces with ChromeVox. 
Google Chrome	69.0.3497.35 (Official Build) dev (64-bit)
Firmware Version	Google_Lulu.6301.136.57

After deleting a download, you can press ctrl + z and it is restored but the screen reader announces nothing. This applies to both deleting individual downloads and clearing all. 

Ctrl+Z is supported in the chrome://downloads page to undo any previous action that has been taken within the same session. This is not a very well known feature, but providing both a confirmation dialog and an "undo" functionality seems redundant.

In bookmarks, when one or more bookmarks are removed, a toast is displayed with an undo button. There is ctrl+z shortcut for undo as well as a redo shortcut. Bookmarks are removed without confirmation.

History shows a confirmation dialog when deleting one or more selected history entries from the toolbar. No confirmation is displayed when deleting a single entry from the item action menu. History has no undo.

It's not clear how to make the pages consistent with each other. They do similar things, but there is no clear better approach. That said, I think we can make two changes to downloads that is similar with what is done on the History and Bookmark Manager pages.

1. Show a confirmation dialog when clearing all download entries.
2. Provide a toast with the number of download entries that were removed along with an undo button.