Remove IE check (and possible compatibility) from beforepaste/paste event switch

Testing whether `beforepaste` is still needed for MSIE9+ is filed as bug 65714.

Bug: 65404
Change-Id: Iff8c4cb97d9c4e0823dd6694dcf9b5ae2a4e011b
Merge "Remove IE check (and possible compatibility) from beforepaste/paste event switch"