Update clipboard permission IDL

Remove 'required' and add default value for allowWithoutGesture.

This change was requested as a follow-up to
https://chromium-review.googlesource.com/c/chromium/src/+/720158

Bug: 
Change-Id: I3260a627ba7efaf2f31151a43ae63ced9d7a55d1
Reviewed-on: https://chromium-review.googlesource.com/742195
Commit-Queue: Gary Kacmarcik <garykac@chromium.org>
Reviewed-by: Jeffrey Yasskin <jyasskin@chromium.org>
Reviewed-by: Daniel Cheng <dcheng@chromium.org>
Cr-Commit-Position: refs/heads/master@{#513348}
1 file changed