Throw DataCloneError on cloning closed Blobs/Files.

Follow the structured cloning spec and disallow cloning of closed Blobs,

 http://www.whatwg.org/specs/web-apps/current-work/#structured-clone

R=mkwst@chromium.org
BUG=344820

Review URL: https://codereview.chromium.org/189623014

git-svn-id: svn://svn.chromium.org/blink/trunk@168746 bbb929c8-8fbe-4397-9dbb-9b2b20218538