Add a flag to hide the download bubble

[opzch]

Description

Add a flag to hide/show the non-dismissible 🡳 in the browser toolbar.

Who's implementing?

• I'm willing to implement this feature myself

The problem

After downloading any file, the 🡳 button appears and cannot be dismissed (unlike the download shelf) without manually clearing the download history or deleting each file on chrome://downloads.

Since --disable-features=DownloadBubble stopped working, it is no longer possible to get rid of it.

If a user has an extension that replaces the download shelf or an external download manager, or just likes Ctrl+J / other keyboard shortcuts, the button is unnecessary.

Possible solutions

Add a flag to hide this button like other menu items

Alternatives

Bring back the download shelf, but it would probably be too invasive and complex
Replace "Full download history" with an option to clear all downloads (related: https://github.com/ungoogled-software/contrib/blob/master/functionality/clear-downloads-button.patch)

Additional context

No response