Intent to ship: File paste support in ClipboardEvent

[Tom Schuster]

In Firefox 116 I intend to enable by default support for pasting a file using the ClipboardEvent, i.e by copying something in your file manager using Ctrl + C and then pasting with Ctrl + V on a webpage. Notably this doesn't cover the clipboard.read() API, which we haven't shipped yet.

Before Electrolysis this theoretically already worked on Windows. File pasting has been enabled in Nightly for almost half a year at this point.

Bug: https://bugzilla.mozilla.org/show_bug.cgi?id=1699743

Standard: https://w3c.github.io/clipboard-apis

Platform coverage: Linux/Mac/Windows (no Android)

DevTools bug: n/a

Other browsers: Supported in Chrome, reportedly also by Safari

Testing: Not testable by WPT, but we have a mochitest (https://bugzilla.mozilla.org/show_bug.cgi?id=1798548)

Secure contexts: available in all contexts (following the ClipboardEvent)