Revert 156826 "Make events propagate to ancestor nodes even if t..."

Caused multiple use-after-frees on ClusterFuzz.

> Make events propagate to ancestor nodes even if the event target is in disconnected DOM trees.
> 
> Fixed the ancient behavior which has been there from WebKit era.
> I couldn't find any reason not to fix an event propagation for disconnected DOM trees.
> Now blink behaves the same way as other browsers.
> 
> BUG=249582
> 
> Review URL: https://chromiumcodereview.appspot.com/23037012

TBR=hayato@chromium.org

Review URL: https://codereview.chromium.org/23523047

git-svn-id: svn://svn.chromium.org/blink/trunk@157575 bbb929c8-8fbe-4397-9dbb-9b2b20218538