Clone form data after dispatching the formdata event


Tests: https://github.com/web-platform-tests/wpt/pull/14814.
commit04d776463564a0566e29895714a9ad78683f1dc4
parent89e7b27ca06eb43c30d9a2bcf84c9965eb9bbcb9
git04d776463564a0566e29895714a9ad78683f1dc4
authorTAMURA, Kent <tkent@chromium.org>
committerAnne van Kesteren <annevk@annevk.nl>
commit timeFri, 11 Jan 2019 10:08:26 +0100